Several American Indian groups originally inhabited the region now known as Wyoming. The Crow, Arapaho, Lakota, and Shoshone were but a few of the original inhabitants encountered when white explorers first entered the region. What is now southwestern Wyoming became nominally a part of the Spanish, and later Mexican, territory of Alta California, until it was ceded to the United States in 1848 at the end of the Mexican-American War. Although French trappers may have ventured into the northern sections of the state in the late 18th century, John Colter, a member of the Lewis and Clark Expedition, first described the region in 1807. At the time, his reports of the Yellowstone area were considered to be fictional. Robert Stuart and a party of five men returning from Astoria discovered South Pass in 1812. The Oregon Trail later followed that route. In 1850, Jim Bridger located what is now known as Bridger Pass, which the Union Pacific Railroad used in 1868—as did Interstate 80, 90 years later. Bridger also explored Yellowstone and filed reports on the region that, like those of Colter, were largely regarded as tall tales at the time.
The region may have acquired the name Wyoming as early as 1865, when Representative J. M. Ashley of Ohio introduced a bill to Congress to provide a "temporary government for the territory of Wyoming". The name Wyoming derives from the Munsee name xwé:wamənk, meaning "at the big river flat", but also named after the Wyoming Valley in Pennsylvania, made famous by the 1809 poem Gertrude of Wyoming by Thomas Campbell.
After the Union Pacific Railroad had reached the town of Cheyenne in 1867, the region's population began to grow steadily, and the federal government established the Wyoming Territory on July 25, 1868. Unlike Colorado to the south, Wyoming enjoyed no significant discovery of such celebrated minerals as gold and silver—nor Colorado's consequent boom in population—although South Pass City experienced a short-lived boom after the Carissa Mine began producing gold in 1867. Moreover, some areas, such as between the Sierra Madre Mountains and the Snowy Range near Grand Encampment, produced copper.
Once government sponsored expeditions to the Yellowstone country were undertaken, the previous reports by men like Colter and Bridger were found to be true. This led to the creation of Yellowstone National Park, which became the world's first national park in 1872. Nearly all of Yellowstone National Park lies within the far northwestern borders of Wyoming.
On December 10, 1869, territorial Gov. John Allen Campbell signed a suffrage act into law, which extended the right to vote to women. And in addition to being the first U.S. state to grant suffrage to women, Wyoming was also the home of other firsts for U.S. women in politics. For the first time, women served on a jury in Wyoming (Laramie in 1870). Wyoming had the first female court bailiff (Mary Atkinson, Laramie, in 1870) and the first female justice of the peace in the country (Esther Hobart Morris, South Pass City, in 1870). Wyoming became the first state in the Union to elect a female governor, Nellie Tayloe Ross, who was elected in 1924 and took office in January 1925. Because of rights given to women, Wyoming earned the nickname of "The Equality State".
Wyoming's constitution included women's suffrage and a pioneering article on water rights. The United States admitted Wyoming into the Union as the 44th state on July 10, 1890.