near Lake Tahoe in 1859 During the winter of 1857–1858, Simpson was ordered to support the military forces assembled for the
Utah War. Simpson's duties included preparing maps for the upcoming campaign, while based at
Fort Leavenworth and
Fort Kearney. On 3 July 1858, Simpson departed for
Camp Floyd, arriving on 19 August. Simpson was ordered to survey a
wagon road between Camp Floyd and
Fort Bridger. Once completed, Simpson was order to make a preliminary reconnaissance into the
Great Salt Lake Desert, which he commenced on 19 October. On 2 May 1859, Simpson led a more extensive expedition consisting of 64 men. His photographer,
Samuel C. Mills, produced the earliest surviving photographs of features along the trail. Simpson's
Central Route played a vital role in the transportation of mail, freight, and passengers between the established eastern states and California, especially when hostilities of the
Civil War closed the
Butterfield Overland Mail stagecoach route that ran along the southern border states.
George Chorpenning immediately switched to Simpson's route to run his existing mail and stage line, and the
Pony Express used it as well. In 1861 the
Transcontinental Telegraph was laid along the route, making the Pony Express obsolete. Afterwards,
Wells Fargo & Co. hauled mail, freight, and passengers along Simpson's route until 1869, when transportation and telegraphy were switched to the newly completed
Transcontinental Railroad. ==Civil War==