National Idaho Day Date in the current year: May 17, 2025

Idaho is a landlocked state in the Pacific Northwest, bordered by Montana, Wyoming, Nevada, Washington State, Oregon, and a small portion of the Canadian province of British Columbia. It is also one of the Mountain States, along with Arizona, Colorado, Montana, Nevada, New Mexico, Utah, and Wyoming.

Idaho’s official name is the Gem State because it is rich in natural resources and produces more than 70 varieties of precious and semi-precious stones, including star garnet (the state gemstone), opal, jasper, and zircon. Its unofficial nicknames, the Potato State and the Spud State, reflect Idaho’s status as the leading producer of potatoes in the United States.

It is estimated that humans may have been in what is now Idaho as early as 14,500 to 16,600 years ago. Native tribes that once dominated the area include the Nez Perce, Coeur d’Alene, Northern and Western Shoshone, and Bannock.

The region was one of the last to be explored by Europeans due to its remoteness. The Lewis and Clark expedition entered present-day Idaho in August 1805, but the region may have been visited earlier by French-Canadian trappers, as evidenced by some tribal names and toponyms that predate the Lewis and Clark expedition.

In the years that followed, Idaho was visited by several fur trading companies: the Missouri Fur Company, the Hudson’s Bay Company, and the North West Company. Fur traders established several forts and trading posts in the region. Missionaries also began to arrive in the region to establish missions and convert local tribes to Christianity.

During the first half of the 19th century, Idaho was part of the Oregon Country, which was jointly occupied by Great Britain and the United States under the Treaty of 1818. The U.S. gained uncontested control of the region in 1846 when Britain and the U.S. signed the Oregon Treaty. The Oregon Territory was formally organized in 1848.

Between 1849 and 1863, parts of present-day Idaho were included in the Oregon, Washington, and Dakota Territories. The Idaho Territory was created in 1862; it included the present-day states of Idaho and Montana, as well as most of Wyoming. The Montana Territory split from the Idaho Territory in 1864, and the Wyoming Territory was created in 1868.

In 1889, Idaho Governor Edward A. Stevenson called for a constitutional convention. The state constitution of Idaho was adopted in November 1889, and Idaho became the 43rd state of the Union on July 3, 1890.

In 2017, National Day Calendar launched the National State Days project to celebrate all states in the order in which they joined the Union, beginning with National Delaware Day on July 13. In this cycle, National Idaho Day falls on May 17. As with all other national state days established by the National Day Calendar, it does not coincide with Idaho’s actual statehood anniversary.