NOTICE TO THE READER. 
The Senate of the United States, and the House of Representatives 
having each ordered ten thousand copies of the reports of the two ex- 
ploring expeditions conducted by me, to be printed together, I have 
deemed it regular and natural to place the report of 1842 first in the order , 
of publication, although heretofore printed; it being first in the order of 
time, and first in the progress of actual exploration. The two reports 
naturally go together, the second being a continuation of the first, and the 
two constituting parts of a whole, which will require a third expedition, 
now commencing, to complete. The first terminated at the Rocky moun- 
tains, and at the two points of greatest interest in that ridge—namely, the 
South Pass, and Frémont’s Peak; the former being the lowest depression 
of the mountains, through which the road to Oregon now passes, and the 
latter the highest elevation, from the base of which four great rivers take 
their rise, and flow in opposite directions, toward the rising and the setting 
sun. The second, after approaching the mountains by a different route, 
connects with the first expedition at the South Pass, and thence finds the 
great theatre of its labors west of the Rocky mountains, and between the 
Oregon river and North California. The third expedition, now com- 
mencing, will be directed to that section of the Rocky mountains which 
gives rise to the Arkansas, the Rio Grande del Norte, and the Rio Colorado 
of California; and will extend west and southwest of that section, so as 
to examine the country towards the Pacific ocean, ascertain the lines of 
communication between the mountains and the ocean in that latitude, and 
complete the examination of the Great Salt lake and of the eens re- 
gion which embosoms it. 
The map which illustrated the report of 1842 is now tdeitica to illus-~ 
trate the entire expedition of 1843-44, so that a view of both expeditions 
will be presented together. This map may have a meager and skeleton 
appearance to the general eye, but is expected to be more valuable to 
science on that account, being wholly founded upon positive data and ac- 
tual operations in the field. About ten thousand miles of actual 
ling and traversing in the wilderness which lies between the frontiers of 
souri and the shores of the Pacific. almost Wes fey eing 
