Thomas Fitzpatrick was an American-American fur trader, Indian agent, and mountain man. He trapped for the Rocky Mountain Fur Company and the American Fur Company. He was among the first white men to discover South Pass, Wyoming. In 1831, he found and took in a lost Arapaho boy, Friday, who he had schooled in St. Louis, Missouri; Friday became a noted interpreter and peacemaker and leader of a band of Northern Arapaho.

South Pass is a route across the Continental Divide, in the Rocky Mountains in southwestern Wyoming. It lies in a broad high region, 35 miles (56 km) wide, between the nearly 14,000 ft (4,300 m) Wind River Range to the north and the over 8,500 ft (2,600 m) Oregon Buttes and arid, saline near-impassable Great Divide Basin to the south. The Pass lies in southwestern Fremont County, approximately 35 miles (56 km) SSW of Lander.