A fast mail service up the Platte River began in 1858 rather than 1857 and was one of two thrusts: a liberalization of the U.S. Post Office's civilian service on Route 8911 (Missouri to Great Salt Lake City) from monthly to weekly service; or the U.S. Army's decision to establish its own special service between Fort Leavenworth, K.T. and Great Salt Lake City (GSLC).
With respect to the former, the change (improvement) in civilian service was necessitated by the fact that the old monthly service between Independence and GSLC was not cutting it, especially in the tense atmosphere of the Utah War, which put a premium on communications since the telegraph wire at that time had been strung only as far west as Booneville, Missouri.
(The whole matter of mail service on Route 8911 during the mid-1850s was one of multiple bones in the Mormon throat, which led to deteriorating LDS-U.S. relations. The decision to take the contract away from W.M.F. Magraw and John M. Hockaday during the summer of 1856 and to give it to a Mormon contractor Hiram Kimball, and the subsequent Post Office decision to unilaterally cancel the Kimball contract effective June 1, 1857 (see note below) was a critical incident that Brigham Young and others harped on for years thereafter as a sign of federal duplicity.)
All during the winter of 1857-58 Col. Albert Sidney Johnston was complaining from the Utah Expedition's Camp Scott, Utah, winter quarters that he had not received any word from the War Dept. (D.C.) or army headquarters (NY) for months. Johnston attributed this absence of mail not only to the winter weather but to the possibility of Mormon interception of the mails. (At the same time the Mormons were grousing that their mail was being tampered with by U.S. postmasters. The issue of who was to be appointed postmaster at GSLC itself became a battleground, and the federal appointee -- Hiram F. Morrell -- became one of the most hated U.S. officials in Utah.)
In the absence of a reliable government mail service the army acted to establish one under their own control. A weekly dispatch was ordered between Fort Leavenworth and Fort Kearney. The army commanders took responsibility for forwarding the dispatches to Fort Laramie, where the pouches were again relayed to the outposts on the Utah territory border.The army enlisted the help of a number of Indian couriers to expedite the flow of communications along the central Overland Route. The army pouches provided the military command with adequate lines of communications but did little to accomodate the soldiers' private correspondence to and from the States. It did nothing for the residents if the Great Salt Lake Valley.
In January 1858 John M. Hockaday left Camp Scott (where he had become U.S. Attorney for Utah) and returned to D.C. in March to lobby for improved Post Office service. He succeeded, traded in his attorney role to resume that of mail contractor, and headed west with a contract to provide weekly service between St. Joseph, Missouri and GSLC. He arrived with the first mail under this new arrangement at Camp Scott in May 1858. Hockaday was not able to make a go of this contract financially and sold out several years later.
Information provided by Bill MacKinnon, September, 2000.
The Brigham Young Carrying and Express Company
The Brigham Young Carrying and Express Company(popularly known as the X.Y. Company) was formed in 1857 to carry the mails "by swift pony express" and to prepare a wagon line to haul freight. A successful bid was made to carry a monthly U. S. mail from Independence to Salt Lake City, and the first mail went through in twenty-six days.
Staging points were set up and a number of regular settlements established along the route, mostly by using labor and materials supplied free by the Saints, at the behest of Brigham Young. A new class of "express missionaries" was created, and these young men were strung out along the trail, outfitted and supplied by wealthier and older members of the church.
Unfortunately, this enterprising development, anticipating in many ways the great express and staging enterprises of the sixties, was brought to an end by the U. S. government's cancellation of the four-year mail contract on June 10, 1857 - barely six months after it had been signed - and by the "Utah War" of 1858, which resulted in the evacuation of all the outposts of Zion outside the Salt Lake Basin and, indeed, a brief "exodus" from the capital itself by its entire Mormon population as the U. S. Army marched in.
Source: Hawgood, John A. America's Western Frontiers: The Exploration and Settlement of the Trans-Mississippi West. 1967.