60 



of this meridian and north of the 46th degree of north latitude have 

 been well examined by Lewis and Clark and under Governor Stevens, 

 and the valuable information they obtained is widely known. The 

 section, however, between the 46th parallel in the north and the 43d 

 in the south, the 106th meridian in the eist, and the dividing line 

 betv/een the waters of the Pacific and the Atlantic in the west, is 

 com[)aratively unknown, except fro n the accounts afforded by trapping 

 parties. The information given of it on the map of Lewis vnd Clark 

 is derived from this latter source ; as is also that on Colonel Bonne- 

 ville's map, published with "Irving's" work on "Adventures in the 

 Rockv Mountains," &c.; and these are our most authe.itic sources of 

 info'.mafcion. These maps have been generally disregarded by subse- 

 quent map-makers ; and previous to the map I compiled for the Pacific 

 Railroad Office, there have been no mountains represented about the 

 fiource of the Yellowstone. From inquiries I made of trappers in 

 1855, I became convinced of the existence of these mountains, and 

 represented them accordingly, endeavoring to combine the information 

 on Lewis and Clark's map and Bonneville's map with that which I 

 had procured from traders and trappers. In doing this, I represented 

 the Big Horn mountains perhap? too far to the west, as they are per- 

 fectly visible from the summit of the Inyan Kara peak, in the Black 

 Hills. 



Leaving out of consideration for the present the smaller detached 

 mountain masses, and beginning with the main range of the Rocky 

 mountains, on the 49th parallel, we find their eastern base to have a 

 direction nearly northwest and southeast, and the range crossing the 

 Missouri at "The Gate of the Mountains." Continuing southeast, it 

 crosses the Yellowstone near where Captain Clark reached that river 

 in 1806, (latitude 46,) just south of which it forms high, snow-covered 

 peaks. This line of mountains is broken through again by the Big Horn 

 river, a id the mountains receive the name of Big Horn mountains. 

 The southeast terminus of the Big Horn mountains sinks into the 

 elevated table land prairie, and tae range perhaps reappears again as 

 the Laramie mountains. (South of the latitude of Fort Laramie the 

 line of the eastern front of the mountains is nearly north and south.) 



The Black Hills, whose geographical position we have determined, 

 are the most eastern portion of what has heretofore been considered a 

 part of the great mountain region west of the Mississippi ; and it ifs 

 ■worthy of note that, if a line be drawn from them to the Little Rocky 

 mountains, on the 48th parallel, which are the most eastern portion 

 in that latitude, this line will be parallel to the line of the main front 

 of the mountains which I have already traced. Wl,at is still more 

 significant is, that if a straight line be drawn from the mouth of the 

 Yellowstone to the mouth of the Kansas river, it will also be parallel 

 to the lines before mentioned, and will have about an equal portion 

 of the Missouri on each side of it. 



The line of the east base of the main mountain mass is the highest, 

 of course, of any portion of the plains, and at Raw Hide peak, near 

 Fort Laramie, is about 5,500 feet elevation, as determined by the 

 horizontally stratified tertiary deposits, though owing to great, denuda- 

 tion the average height there of this line of the plains will not be so great 



