The brothers Francois and Louis Joseph Vérendrye, French-Canadian explorers, may have entered Wyoming in 1743. However, the first recorded exploration was that of John Colter, a former member of the Lewis and Clark expedition. He is thought to have reached what is now Yellowstone Park during 1807–08. Traders and trappers followed and established a flourishing fur trade. Fort Laramie was built in 1834 as a trading post. James Bridger founded Fort Bridger in southwestern Wyoming in 1843.

The fur trade began to decline in the late 1830's, because of overtrapping and a decrease in demand for beaver. At about the same time, wagon trains carrying settlers west began crossing Wyoming. Hundreds of thousands of people passed through the area on their way to the Pacific Northwest over the Oregon Trail, to California over the California and Overland trails, and to the Salt Lake Valley over the Mormon Trail. (

Few of these early settlers remained in Wyoming, mainly because there was better farmland elsewhere. Also there were troubles with the Plains Indians, whose homeland had been disturbed first by the traders and now by the steady stream of prairie schooners. For protection, the federal government ordered army troops to be stationed in forts along the trails. Indian raids continued, however, climaxing in 1866–68 in what is often called Red Cloud's War. (