Fort Laramie played an integral role in the development of the American West. It began as a private fur trading post owned by William Sublette and Robert Campbell in 1834. The original name of the post was Fort William, but it came to be known as “Laramie” since it was near the Laramie and North Platte Rivers. The American Fur Company bought the fort in 1836, when the fort was renamed Fort John but still commonly known as Fort Laramie. It was one of the major trading centers in the Rocky Mountains, where Indians and fur traders came to barter and exchange goods. In 1849 the military bought the post for the protection of immigrants who crossed the plains. Fort Laramie became the most important supply depot for travelers on the Oregon and California trails, and it is estimated that between 1843 and 1863 some 200,000 immigrants passed through the fort. Immigrants included California gold rushers and the first bands of Mormons led by Brigham Young.

Alarmed by the increasing encroachment on their hunting grounds, ten thousand Sioux, Cheyenne, Arapaho, and Crow Indians met with United States Commissioners near Fort Laramie in the summer of 1851 to draw up a treaty concerning the military’s use of their land. In spite of the treaty, numerous outbreaks of violence occurred between Native Americans and the military near the fort, including the Grattan Massacre in 1854 and the Fetterman Massacre in 1866. Military campaigns, many organized at Fort Laramie, continued against the Sioux and Cheyenne into 1876.

By 1890 the importance of the fort had diminished as the threat from Native Americans decreased and homesteaders began settling the region. The post was abandoned in 1890, and many buildings were torn down or left to decay. A campaign to restore the old fort began in the 1930s, and the National Park Service established it as a national monument in 1938. It was re-designated as a national historic site in 1960.