The Gold Rush brought hundreds of thousands of people into California and many of them wanted a way to more quickly get mail and packages out east so these men devised a plan which would include 120 riders, 184 stations (post offices), and 400 horses. Buffalo Bill was one of their first riders.
Wagons were limited as to where they could go but horses could make more of a straight path in any direction. It doesn't sound so good now, but the Pony Express could go from coast to coast in 10 days. The operation was halted several times as riders were getting killed by Indians and of course mail and packages were taken.
The cost for sending packages was extremely expensive ($155 in today's dollars), then the price quickly went down to $31.10 as they were trying to find a price point that would be more acceptable but still allow them to make money. Unfortunately for them, cable lines were run across the country and the telegraph took away much of their business so they went under.
Wells Fargo bought their logo. In 1992, Congress designated The Pony Express Trail as a National Historic Trail, and the U.S. Postal Service trademarked the words: "Pony Express," in 2006.