Idaho is admitted to the union on July 3, 1890.

Exploration of the North American continent mostly proceeded inward from the Atlantic and Pacific coasts and northward from Spanish Mexico. Therefore, the rugged territory that would become Idaho long remained untouched by Spanish, French, British and American trappers and explorers. Even as late as 1805, Idaho Native Americans like the Shoshone had never encountered Europeans.

That changed with the arrival of the American explorers Meriwether Lewis and William Clark in the summer of 1805. Searching for a route over the Rocky Mountains to the Columbia River, Lewis and Clark traveled through Idaho with the aid of the Shoshone and their horses. British fur traders and trappers followed a few years later, as did missionaries and a few hardy settlers. As with many remote western states, large-scale settlement began only after gold was discovered. Thousands of miners rushed into Idaho when word of a major gold strike came in September 1860, occupying Indigenous lands. Merchants and farmers followed, eager to make their fortunes “mining the miners.”

By 1880, Idaho boasted a population of 32,610. In the southern section of the territory, many settlers were followers of The Church of Jesus Christ of Latter-day Saints who had been dispatched from Salt Lake City to found new colonies. Increasingly, Idaho territory became divided between an LDS-dominated south and an anti-LDS north. In the mid-1880s, anti-LDS Republicans used widespread public antipathy toward the practice of polygamy to pass legislation denying the predominantly Democratic Latter-Day Saints the vote.

With the Democratic vote disarmed, Idaho became a Republican-dominated territory. National Republicans eager to increase their influence in the U.S. Congress began to push for Idaho statehood in 1888. The following year, the Idaho territorial legislature approved a strongly anti-LDS constitution. The U.S. Congress approved the document on this day in 1890, and Idaho became the 43rd state in the Union.