1837, the garrison was drastically reduced due to the Second Seminole War in Florida Territory, and many soldiers in the First Infantry Regiment left the fort with unpaid credits. In 1835, Sibley started lobbying for the establishment of a post office at Fort Snelling with regular service from Prairie du Chien, contacting his political connections in Michigan Territory for support. He succeeded, and the American Fur Company's Western Outfit secured the contract for mail delivery from 1837 to 1839. Mail was carried by steamboats during the summer, but during the long winter, Sibley and his partners had to hire runners, and found it difficult to deliver the mail on time. Land cession treaties of 1837 The financial panic of 1837 nearly resulted in a collapse of the U.S. banking and monetary system, triggering an economic depression which lasted until the mid-1840s. Fur prices fell sharply and muskrat pelts, which made up the bulk of the fur trade in Sibley's region, were no longer in demand. By February 1838, Crooks reported to Sibley that the previous year's pelts were still sitting in a New York warehouse, and had become essentially worthless. The partners of the American Fur Company were on the brink of financial ruin. However, in the summer and fall of 1837, the United States government signed three major treaties with the Ojibwe, Dakota and Winnebago tribes, in which they agreed to give up all their lands east of the Mississippi River in return for compensation. Sibley and the American Fur Company partners aimed to collect payment from the government to cover a substantial portion of their business losses, which appeared on their books as "Indian debts." In December 1836, Sibley had written to American Fur Company president Ramsay Crooks urging him to lobby his Washington connections to prevent Indian agent Lawrence Taliaferro, a long-time political enemy of the traders, from being appointed as treaty commissioner the following year. Taliaferro nevertheless prevailed. On July 29, 1837, Henry Sibley was a signatory to the U.S. treaty with the Ojibwe, also known as the Treaty of St. Peters, the Treaty with the Chippewa, or the "White Pine Treaty". The Ojibwe treaty named his business partner Hercules L. Dousman as one of three fur traders to receive debt payments. Agent Taliaferro, infuriated by what he viewed as trader meddling when the Ojibwe treaty was signed at Fort Snelling, moved the Mdewakanton Dakota treaty