Niobrara River-North Platte River drainage divide area landform origins, eastern Wyoming and western Nebraska, USA

Authors

A geomorphic history based on topographic map evidence

Abstract:

The Niobrara River-North Platte River drainage divide area is located in eastern Wyoming and western Nebraska, USA. Although detailed topographic maps of the Niobrara River-North Platte River drainage divide area have been available for more than fifty years detailed map evidence has not previously been used to interpret the region’s geomorphic history. The interpretation provided here is based entirely on topographic map evidence. The Niobrara River-North Platte River drainage divide area is interpreted to have been eroded during immense southeast-oriented flood events, the first of which flowed on a topographic surface at least as high as the highest points in the present-day drainage divide area. Flood erosion ended when headward erosion of the east-oriented Cheyenne River valley captured all southeast-oriented flood flow.

Preface:

The following interpretation of detailed topographic map evidence is provided as evidence in the Missouri River drainage basin landform origins research project, which is compiling similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with and within certain adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored geomorphology paradigm, which is briefly described in the introduction below. Project essays are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.

Introduction:

  • The purpose of this essay is to use topographic map interpretation methods to explore eastern Wyoming and western Nebraska Niobrara River-North Platte River drainage divide area landform origins. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays and then by leaving a link to those essays in a comment here.
  • This essay is also exploring a paradigm in which erosional landforms are interpreted as evidence left by immense glacial melt water floods. Implied in that interpretation is the immense floods were derived from a thick North American ice sheet that created a deep “hole” in the North American continent and also melted fast. The previously unexplored paradigm being tested in this and similar essays is a thick North American ice sheet, comparable in thickness to the present day Antarctic ice sheet, occupied approximately the North American region usually recognized to have been glaciated and through its weight and erosive actions created a “deep” North American “hole”, through its weight and deep erosion (and perhaps deposition) along major south-oriented melt water flow routes caused significant crustal warping and tectonic change, through its action of melting fast produced immense floods that flowed across the continent, and through its action of melting fast systematically opened up space in the ice sheet created “hole” so headward erosion of newly developed north-oriented drainage systems captured immense south-oriented melt water floods and diverted immense melt water floods north into space the ice sheet had once occupied.
  • If this previously unexplored paradigm is correct the geographic region explored by this essay should contain evidence of immense floods that were captured by headward erosion of new valley systems so as to cause the floods to flow in a different direction. Ability of this previously unexplored paradigm to explain Niobrara River-North Platte River drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Niobrara River-North Platte River drainage divide area general location map

Figure 1: Niobrara River-North Platte River drainage divide area general location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a general location map for the western Nebraska and eastern Wyoming Niobrara River-North Platte River drainage divide area. The state of Nebraska is enclosed by the yellow boundary line in the figure 1 southeast quadrant, the state of South Dakota is enclosed by the red boundary line in the northeast quadrant, and the state of Wyoming is in the figure 1 west half and is west of the purple boundary line. The Niobrara River originates west of Lusk, Wyoming and flows in a southeast, east, and northeast direction across northwestern Nebraska to the figure 1 east edge. East of figure 1 the Niobrara River flows east and southeast before turning north to join the east and southeast oriented Missouri River. The North Platte River flows northeast to Casper, Wyoming (located along the figure 1 west center edge) and then east and southeast through Douglas, Glendo, Guernsey, Fort Laramie, Lingle and Torrington, Wyoming and to Morrill, Mitchell, and Scottsbluff, Nebraska. The Niobrara River-North Platte River drainage divide area discussed here is located south of the Niobrara River source near Manville, Wyoming and continues east to approximately the location of north-south highway 29 in western Nebraska (between Harrison and Mitchell, Nebraska). Significant areas in the region of this Niobrara River-North Platte River drainage divide area are not well-drained and have limited topographic map evidence that can be used to interpret the region’s drainage history. This essay relies on what limited evidence is available. North and west of the Niobrara River-North Platte River drainage divide area is the Cheyenne River drainage basin, or more specifically the drainage basin of northeast-oriented Lightning Creek, which flows to the Cheyenne River, which in turn flows around the Black Hills south end and then turns northeast. North-oriented Lance Creek is immediately west of the Niobrara River source area and flows to northeast-oriented Lightning Creek. Landform evidence illustrated here is interpreted in the context of an immense southeast-oriented flood flowing across the entire figure 1 map area and which was systematically captured and diverted east and northeast by headward erosion of deep valleys eroded into a topographic surface at least as high as the figure 1 region highest elevations today. In the figure 1 map region headward erosion of the North Platte River valley first captured the southeast-oriented flood flow and then headward erosion of the east, southeast and northeast-oriented Niobrara River valley captured southeast-oriented flood flow moving to what was then an actively eroding and newly eroded southeast-oriented North Platte River valley. Detailed maps below provide evidence supporting this interpretation. Evidence of southeast-oriented flood flow in adjacent regions is described in other essays describing Niobrara River drainage divides (see essays under Niobrara River on sidebar category list) and also in essays for drainage basins north and west of the Niobrara River drainage basin (for example, see essays under White River or Cheyenne River on sidebar category list). The White River and the Cheyenne River drainage basins are the major drainage basins immediately to the north of the Niobrara River drainage basin.

Niobrara River-North Platte River drainage divide area detailed location map

Figure 2: Niobrara River-North Platte River drainage divide area detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a detailed location map for the Niobrara River-North Platte River drainage divide area. Platte and Goshen Counties are located in Wyoming. Sioux and Scotts Bluff Counties are located in Nebraska. The Niobrara River originates south and north of Manville, Wyoming and flows through Lusk and Van Tassell, Wyoming before turning southeast to flow to the Agate Fossil Beds National Monument in Sioux County, Nebraska. The North Platte River enters the figure 2 map area in the northwest corner and flows southeast  to the Glendo Reservoir and then through Guernsey, Fort Laramie, and Torrington, Wyoming before flowing into Scotts Bluff County in Nebraska. The Niobrara River-North Platte River drainage divide area discussed here is located east of the highway extending north from Guernsey, Wyoming to Manville, Wyoming and west of the highway extending north from Mitchell, Nebraska to Harrison, Nebraska. Note the southeast tributaries flowing to south-southeast-oriented Rawhide Creek, which is the primary drainage system located in the Niobrara River-North Platte River drainage divide area discussed here. These southeast-oriented tributary valleys were probably initiated as interconnected channels in a large southeast-oriented anastomosing channel complex formed during an immense southeast-oriented flood, which was first captured by headward erosion of the North Platte River-Rawhide Creek valley and subsequently beheaded by headward erosion of the Niobrara River valley and the valleys of north-oriented Niobrara River tributaries. East of the Rawhide Creek basin, especially in the state border region, sand dunes obscure topographic map evidence needed to determine drainage histories. While the sand dunes obscure some desired topographic map evidence, the sand hills provide evidence large amounts of sandy sediment were deposited in the figure 2 map region. Further north in North Dakota and Manitoba for example, sand dune regions are developed on sandy deltas where large glacial melt water floods entered what are usually considered to have been large standing bodies of water (or lakes). Evidence presented here is not adequate to determine whether or not the Niobrara River-North Platte River drainage divide area sand dunes are developed on such a deltaic deposit, although evidence presented in this essay and in other essays makes a strong case for an immense southeast-oriented flood moving to and across the present day Niobrara River-North Platte River drainage divide region.

Niobrara River headwaters area at Page Flat Draw

Figure 3: Niobrara River headwaters area at Page Flat Draw. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates one of the Niobrara River headwaters areas south of Manville, Wyoming. Of particular interest is Page Flat Draw, which begins as northwest oriented King Draw and Page Flat Draw before turning northeast to drain to the north end of the Wanker Hills and then turning southeast in the figure 3 center to drain to Silver Springs Creek, which flows to the southeast-oriented Niobrara River east of the figure 3 map area. Note how northwest oriented King Draw is linked by a through valley with north-oriented Woods Ranch Draw, which joins Page Flat Draw at the Wanker Hills north end. The King Draw-Woods Ranch Draw through valley is just one of several such through valleys crossing the Wanker Hills upland. These dry valleys or wind gaps were eroded by southeast-oriented flood waters, which were captured by headward erosion of the south-oriented Rawhide Creek valley from what was then the actively eroding and deep North Platte River valley to the south (figure 4 below illustrates the Rawhide Creek headwaters location). Subsequently headward erosion of the Niobrara River valley and its tributary Silver Springs Creek valley and Page Flat Draw valley captured the southeast-oriented flood flow and caused a reversal of flood flow on the north end of a south-oriented flood flow route to what was then the actively eroding Rawhide Creek valley, which eroded the present day north-oriented Woods Ranch Draw valley, and also caused a reversal of flood flow on the northwest end of a southeast-oriented flood flow route to what was then the actively eroding south-oriented Rawhide Creek valley to create what is today the northwest oriented King Draw-Page Flat Draw headwaters valley. Note the unnamed northwest- and northeast-oriented Niobrara River tributary south of Manville that originates just northwest of the northwest-oriented Page Flat Draw valley segment. That unnamed tributary valley eroded southwest from what was then the actively eroding Niobrara River valley head to capture southeast-oriented flood flow moving to the newly eroded Page Flat Draw valley. The northwest-oriented headwaters valley of that unnamed tributary was eroded by reversed flood flow on the northwest end of the beheaded flood flow route.

Page Flat Draw-Rawhide Creek drainage divide area

Figure 4: Page Flat Draw-Rawhide Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Page Flat Draw-Rawhide Creek and the Woods Ranch Draw-Rawhide Creek drainage divide areas south of figure 3 and includes overlap areas with figure 3. The through valley linking northwest oriented King Draw and Page Flat Draw with north-oriented Woods Ranch Draw is located in the figure 4 north center. Rawhide Creek originates in the west-to-east oriented wind gap or through valley located just north of the Niobrara County-Goshen County line in the figure 4 center. Note, the west end of that wind gap or through valley is drained by a northwest and southwest-oriented stream flowing to northwest-oriented Willow Creek that has a southeast and south-oriented tributary draining to the west-to-east oriented through valley from the north (Willow Creek after flowing northwest turns southwest and eventually reaches the North Platte River). The west-to-east oriented through valley is evidence flood waters once crossed the north-south range of hills (known in the north as Wanker Hills and in the south as Wildcat Hills) on a topographic surface at least as high as the highest figure 4 elevations today (although the region may have been uplifted during and/or after the flood). Note how through valleys link the northwest-oriented Page Flat Draw headwaters with southeast oriented valleys to the west-to-east oriented through valley in which Rawhide Creek headwaters flow (e.g. southeast oriented Lamb Draw in the figure 4 center). These higher level northwest-to southeast oriented through valleys provide evidence water once flowed southeast from the Page Flat Draw drainage basin to the Rawhide Creek drainage basin. Further west, the southeast and south-oriented tributary to the stream draining the west end of the west-to-east oriented through valley to Willow Creek is linked by a northwest-southeast oriented through valley to a northwest-oriented tributary to southwest-oriented Muddy Creek (located west of figure 4), which drains to the North Platte River. Those drainage features provide evidence a southeast oriented flood flow route was first captured by headward erosion of the southeast and east oriented Rawhide Creek valley, then captured by headward erosion of the Willow Creek valley, and finally captured by headward erosion of the Muddy Creek valley, which caused a reversal of flood flow on the northwest end of the beheaded southeast-oriented flood flow route to erode the present day northwest-oriented Muddy Creek tributary valley. Many other figure 4 examples can be cited including the north-south through valley linking north-oriented Woods Ranch Draw with south-oriented Aego Creek, which once was a south-oriented valley, but the north end was reversed when south-oriented flood flow was beheaded.

Detailed map of Page Flat Draw-Rawhide Creek drainage divide area

Figure 5: Detailed map of Page Flat Draw-Rawhide Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 provides a detailed map of the Page Flat Draw-Rawhide Creek drainage divide area seen in less detail in figure 4 above. Page Flat Draw headwaters are located in the figure 5 northwest corner and are linked by a through valley to a southwest-oriented Willow Creek tributary valley. Rawhide Creek flows east and southeast across the figure 5 south center edge. Lamb Draw drains south to Rawhide Creek in the figure 5 south center. Note the through valley linking south-oriented Lamb Draw with north oriented Page Flat Draw and also the north-south through valleys on either side of Lamb Draw. Also note through valleys linking south-oriented New Hampshire Draw with north-oriented valleys, and further east the through valley linking a south-oriented Aego Creek tributary with a northeast-oriented Silver Springs Creek tributary valley. These multiple through valleys not only provide evidence flood waters once flowed south across the region, they also provide evidence the flood waters were eroding anastomosing channels into the underlying bedrock as they deeply eroded the figure 5 landscape and surrounding region. A high level topographic surface at least as high as the highest figure 5 elevations today was first eroded by headward erosion of what was then the deep south-oriented Rawhide Creek valley and its deep south-oriented tributary valleys. Flood flow to those south-oriented Rawhide Creek tributary valleys was then progressively captured by headward erosion of deep north- and northeast-oriented valleys from what was then the actively eroding deep Niobrara River valley to the north. Probably the first deep north-oriented valleys to erode into the figure 5 map area were the unnamed northeast-oriented Silver Springs Creek tributary valley followed by the northeast-oriented Silver Spring Creek valley (both located in the figure 5 northeast corner area). Note how the northeast-oriented Silver Springs Creek valley captured southeast and south-oriented  flood waters that had been flowing south to the what was then the actively eroding south-oriented New Hampshire Draw valley. Subsequently headward erosion of east-oriented Page Flat Draw north of the figure 5 map area beheaded the south-oriented flood flow routes, causing reversals of flood flow to create the present day Page Flat Draw-Rawhide Creek drainage divide.

Muskrat Creek headwaters area

Figure 6: Muskrat Creek headwaters area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates an area south of the figure 4 map area to document additional evidence that southeast-oriented flood waters once crossed the Wanker Hills-Wildcat Hills upland region (there is some overlap with figure 4). In particular note the through valley eroded across the Wildcat Hills where the east end is labeled Muskrat Canyon. Note how Muskrat Creek originates in a southwest-oriented tributary valley to that west to east oriented through valley (or wind gap) and then turns east to flow through northeast-oriented Muskrat Canyon before turning south and southeast to eventually join southeast-oriented Rawhide Creek. A southeast-oriented through valley in the figure 6 north center links the Muskrat Creek headwaters with southeast-oriented Negro Baby Creek, which flows somewhat more directly to southeast-oriented Rawhide Creek. Extending that through valley to the northwest across the southwest-oriented Muskrat Creek headwaters leads to the northwest oriented headwaters of Willow Creek (see figure 4), which after flowing northwest turns southwest and eventually reaches the North Platte River. Note how the west end of the Muskrat Canyon west-to-east oriented through valley is drained by northwest, west, and south-oriented Miller Draw, which eventually drains to the North Platte River. The drainage history recorded by this figure 6 evidence (and additional figure 6 evidence like it) describes a southeast-oriented flood flowing across the entire figure 6 map area on a topographic surface at least as high as the highest figure 6 elevations today (although the region may have been uplifted during and/or following the flood). Headward erosion of the deep southeast-oriented Rawhide Creek valley and its deep tributary valleys, such as the southeast-oriented Muskrat Creek valley and the Negro Baby Creek valley, eroded the region east of the Wildcat Hills and began eroding deep valleys into and across the Wildcat Hills. Subsequently headward erosion of deep south-oriented valleys (including the Willow Creek valley) from what was then the deep and actively eroding North Platte River valley headcut west of the Wildcat Hills then progressively and systematically captured southeast-oriented flood flow routes crossing the Wildcat Hills and diverted the flood waters south to the newly eroded North Platte River valley. By capturing the southeast-oriented flood waters flood flow routes across the Wildcat Hills were beheaded, with flood waters on the west and northwest ends of those beheaded flood flow routes reversing flow direction to flow west and/or northwest to the newly eroded south-oriented valleys west of the Wildcat Hills. In process the captured flood waters eroded the region west of the Wildcat Hills.

Detailed map of Muskrat Creek headwaters area

Figure 7: Detailed map of Muskrat Creek headwaters area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 provides a detailed map of the Muskrat Creek headwaters area illustrated in less detail in figure 6 above. Note how Muskrat Creek originates as a southwest-oriented stream and then turns east and northeast to flow through Muskrat Canyon before turning southeast. Also note how the Muskrat Creek headwaters are linked by a through valley with southeast-oriented Little Wildcat Canyon, which drains to southeast-oriented Negro Baby Creek. Also note how west and northwest-oriented Willow Creek headwaters are linked by higher level through valleys with southwest-oriented Muskrat Creek headwaters and the southeast-oriented Little Wildcat Canyon. Unnamed Miller Draw drains northwest and west in the figure 7 southwest corner (and has a southwest-oriented tributary draining from the figure 7 west center) and west of figure 7 turns south. The Muskrat Canyon through valley and the Little Wildcat Canyon through valley (with its link to northwest-oriented Willow Creek) provide evidence flood waters were eroding ever-changing anastomosing channels across the figure 7 map region. As one channel eroded deeper it captured flood waters from adjacent and interconnected channels. These captures beheaded flood flow on other flood flow channels, which caused flood waters on ends of the beheaded flood flow routes to reverse their flow direction. The anastomosing channels in the figure 7 map area were probably deep valleys being eroded into the Wildcat Hills area. Southeast-oriented flood flow across the figure 7 map area eroded an ever-changing pattern of deep anastomosing channels as the deep southeast-oriented Muskrat Creek, Negro Baby Creek, and other Rawhide Creek tributary valleys eroded headward into the Wildcat Hills region. For a time flood waters probably flowed southeast along the Willow Creek valley to the Little Wildcat Canyon and east into the Miller Draw valley, where flood waters split, with some water going northeast to the Little Wildcat Canyon valley and some water going east to the Muskrat Creek Canyon valley. Subsequently the Muskrat Canyon valley was eroded deeper and captured flood flow first from the Willow Creek route and later from the Little Wildcat Canyon route. Still later headward erosion of south-oriented valleys west of the Wildcat Hills captured southeast-oriented flood flow west of the Wildcat Hills, causing a reversal of flow in what is today the west-oriented Miller Draw valley.

Niobrara River tributaries south of Van Tassell, Wyoming

Figure 8: Niobrara River tributaries south of Van Tassell, Wyoming. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the Niobrara River valley and Niobrara River tributaries in the Van Tassell, Wyoming area, which is located along the Wyoming-Nebraska border. The Niobrara River flows east-southeast to Van Tassell and then turns southeast to flow to the figure 8 southeast corner. Niobrara River tributary valleys are southeast-oriented, although drainage is not well-developed in much of the figure 8 region. Based on the available evidence figure 8 region landscape features were eroded by multiple southeast-oriented flood flow channels and the deep Niobrara River valley eroded headward to capture flood flow from those southeast-oriented flood flow channels. The only well-defined drainage divide to interpret here is between the southwest-oriented valley extending from the figure 8 northeast corner to the southeast-oriented Niobrara River and tributary valleys draining southeast to the Niobrara River (located east of the Niobrara River). Headward erosion of the southwest-oriented valley beheaded southeast-oriented flood flow routes that were eroding the Niobrara River tributary valleys to the northwest. Orientations of drainage routes that can be determined from the figure 8 evidence are otherwise almost all southeast oriented and support the interpretation that figure 8 map region landscape features were eroded by southeast-oriented flood waters.

Pine Ridge Creek-Rawhide Creek drainage divide area

Figure 9: Pine Ridge Creek-Rawhide Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Pine Ridge Creek-Rawhide Creek drainage divide area north of Lingle, Wyoming and northeast of Fort Laramie, Wyoming. The southeast oriented North Platte River is located south of Fort Laramie in the figure 9 southwest corner. Rawhide Creek flows southeast from the figure 9 north center to the figure 9 east center and then turns south to join the North Platte River at Lingle (located south of the figure 9 map area). Pine Ridge Creek originates northwest of Pine Ridge (in the figure 9 center) and flows northwest before turning southwest to flow to the North Platte River west of Fort Laramie. Note northwest-oriented tributaries flowing to the southwest-oriented Pine Ridge Creek valley segment and southeast oriented tributaries flowing to south-oriented Rawhide Creek. These southeast and northwest oriented tributaries are evidence the Rawhide Creek valley eroded north across multiple southeast-oriented flood flow routes, such as might be found in anastomosing channels, to capture the flood waters and divert the water south to what was probably an actively eroding North Platte River valley headcut. Subsequently, as the North Platte River valley headcut eroded northwest the southwest-oriented Pine Ridge Creek valley was able to erode northeast to capture some of those same southeast oriented flood flow routes and divert the water southwest to what was then the newly eroded North Platte River valley. The northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of the beheaded flood flow routes.

Rawhide Creek-Sheep Creek drainage divide area

Figure 10: Rawhide Creek-Sheep Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates the Rawhide Creek-Sheep Creek drainage divide area north of Torrington, Wyoming. The north-south orange line near the figure 10 east edge is the Wyoming-Nebraska state line. Rawhide Creek is the southeast and south-oriented stream located in the figure 10 southwest corner. Sixteenmile Creek flows northwest, southwest and south-southwest to join Rawhide Creek. Note northwest-oriented Sixteenmile Creek headwaters and tributary streams. Also note the unnamed southwest-oriented Rawhide Creek tributary just southeast of Sixteenmile Creek, which also has northwest-oriented tributaries. Sheep Creek originates northwest of Spoon Butte and flows southeast to the figure 10 southeast corner area. Sheep Creek flows south to join the North Platte River just east of the state line and east of Torrington, Wyoming. Note the southeast-oriented Sheep Creek headwaters and southeast-oriented Sheep Creek tributaries. The southeast-oriented Sheep Creek tributaries and headwaters provide evidence the south-oriented Sheep Creek valley eroded headward to capture multiple southeast-oriented flood flow routes, such as might be found in a southeast-oriented anastomosing channel complex. The northwest-oriented tributaries and headwaters of the unnamed southwest-oriented Rawhide Creek tributary and southwest-oriented Sixteenmile Creek provide evidence the Rawhide Creek valley eroded north and the unnamed tributary valley eroded northeast to capture southeast-oriented flood flow routes moving water to the southeast-oriented Sheep Creek tributary valleys, and the Rawhide Creek valley and Sixteenmile Creek valley eroded north and northeast to capture southeast-oriented flood flow to the unnamed Rawhide Creek tributary valley and to additional Sheep Creek tributaries, including the Sheep Creek headwaters. The northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of the beheaded southeast-oriented flood flow channels.

Additional information and sources of maps studied

This essay has provided only a sample of the detailed topographic map evidence supporting the flood erosion interpretation. Many additional illustrations could be provided. Readers are encouraged to look at mosaics of detailed topographic maps to see the abundance of available data. Maps used in this study were created and published by the United States Geologic Survey and can be obtained directly from the United States Geological Survey and/or from dealers offering United States Geological Survey maps. Hard copy maps can also be observed at United States Geological Survey map depositories which are located throughout the United States and elsewhere. Illustrations used here were created using National Geographic Society TOPO software and digital map data. TOPO software and map data can be obtained from the National Geographic Society and/or dealers offering National Geographic Society digital map data.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: