Idaho is admitted to the union on this day in 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 Indians like the Shoshone had never encountered a white man.
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 Indians 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. 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 Mormons who had been dispatched from Salt Lake City to found new colonies. Increasingly, Idaho territory became divided between a Mormon-dominated south and an anti-Mormon north. In the mid-1880s, anti-Mormon Republicans used widespread public antipathy toward the Mormon practice of polygamy to pass legislation denying the predominantly Democratic Mormons the vote.
With the Democratic Mormon 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-Mormon constitution. The U.S. Congress approved the document on this day in 1890, and Idaho became the 43rd state in the Union.