The party spent the rest of 1823 wintering in the Wind River Valley. In 1824, Smith sent an expedition to find an expedient route through the Rocky Mountains. Smith was able to retrieve information from Crow natives. When communicating with the Crows, one of Smith's men made a unique map (consisting of buffalo hide and sand), and the Crows were able to show Smith and his men the direction to the South Pass. Smith and his men crossed through this pass from east to west and encountered the Green River near the mouth of the Big Sandy River in what is now Wyoming. The group broke into two parties—one led by Smith and the other by Thomas Fitzpatrick—to trap upstream and downstream on the Green. The two groups met in July on the Sweetwater River, and it was decided that Fitzpatrick and two others would take the furs and the news of the identification of a feasible highway route through the Rockies to Ashley in St. Louis. Scottish-Canadian trapper Robert Stuart, employed by John Jacob Astor's Pacific Fur Company, had previously discovered the South Pass, in mid-October 1812, while traveling overland to St. Louis from Fort Astoria, but this information was kept secret. Smith later wrote a letter to Secretary of War John Eaton in 1830 making the location of the South Pass public information.