Forming part of the Pacific Northwest (and the associated Cascadia bioregion), Idaho is divided into several distinct geographic and climatic regions.

The state's south includes the Snake River Plain (which has most of the population and agricultural land), and the southeast incorporates part of the Great Basin.

Excavations at Wilson Butte Cave near Twin Falls in 1959 revealed evidence of human activity, including arrowheads, that rank among the oldest dated artifacts in North America.

American Indian peoples predominant in the area included the Nez Percé in the north and the Northern and Western Shoshone in the south.

[17]An early presence of French-Canadian trappers is visible in names and toponyms: Nez Percé, Cœur d'Alène, Boisé, Payette.

Some of these names appeared prior to the Lewis and Clark and Astorian expeditions, which included significant numbers of French and Métis guides recruited for their familiarity with the terrain.

The Lewis and Clark expedition crossed Idaho in 1805 on the way to the Pacific, and in 1806, on the return trip, largely following the Clearwater River in both directions.

The first non-indigenous settlement was Kullyspell House, established on the shore of Lake Pend Oreille in 1809 by David Thompson of the North West Company for fur trading.

[19][20] In 1812 Donald Mackenzie, working for the Pacific Fur Company at the time, established a post on the lower Clearwater River near present-day Lewiston.

[30] Between 1991 and 2002, Idaho expanded its commercial base to include the science and technology sector which accounted for over 25% of its Gross state product in 2001.

Although the state's western border is about 330 miles (530 km) from the Pacific Ocean, the maritime influence is still felt in Idaho; especially, in the winter when cloud cover, humidity, and precipitation are at their maximum extent.

This influence has a moderating effect in the winter where temperatures are not as low as would otherwise be expected for a northern state with predominantly high elevations.

[41] The maritime influence is least prominent in the state's eastern part where the precipitation patterns are often reversed, with wetter summers and drier winters, and seasonal temperature differences are more extreme, showing a more semi-arid continental climate.

[42] Idaho can be hot, although extended periods over 98 °F (37 °C) are rare, except for the lowest point in elevation, Lewiston, which correspondingly sees little snow.

[50] Nampa, about 20 miles (30 km) west of downtown Boise, became the state's second largest city in the late 1990s, passing Pocatello and Idaho Falls.

Most of Idaho's white residents trace their ancestry to the United Kingdom, Germany, Ireland, France, Italy, or Poland.

[63] Note: Births in table don't add up, because Hispanics are counted both by their ethnicity and by their race, giving a higher overall number.

[79] In 2022, the Public Religion Research Institute's American Values Survey estimated altogether, 72% of the population was Christian, 26% were religiously unaffiliated, and 3% were New Agers.

The same vast tracts of unspoiled wilderness that attracted Ernest Hemingway to the region in the early 1960s continue to provide outdoor enthusiasts with excellent camping, hunting, fishing, as well as whitewater kayaking and rafting, and skiing.

The Burlington Northern Santa Fe (BNSF) connects the Idaho Panhandle with Seattle, Portland, and Spokane to the west, and Minneapolis and Chicago to the east.

The Union Pacific Railroad also crosses southern Idaho traveling between Portland, Oregon, Green River, Wyoming, and Ogden, Utah, and serves Boise, Nampa, Twin Falls, and Pocatello.

This led to sometimes-bitter clashes between the two parties, including a range war with the Democrats backing the sheepherders and the Republicans the cattlemen, which ended in the "Diamondfield" Jack Davis murder trial.

Several Idaho Democrats have had electoral success in the U.S. House of Representatives over the years, but the Senate delegation has been a Republican stronghold for decades.

Even in that election, Lyndon B. Johnson defeated Barry Goldwater in the state by fewer than two percentage points, compared to a landslide nationally.

Only Blaine County, which contains the Sun Valley ski resort, supported John Kerry, who owns a home in the area.

Pending the outcome of a legal challenge on a bill passed on 20 March 2023, authorized methods of execution include the firing squad.

[122] Central Idaho is home to one of North America's oldest ski resorts, Sun Valley, where the world's first chairlift was installed in 1936.

The Boise Open professional golf tournament has been played at Hillcrest Country Club since 1990 as part of the Korn Ferry Tour.

In 2016, Meridian's Michael Slagowski ran 800 meters in 1:48.70, one of the 35 fastest times ever run by a high school boy in the United States.

[125] Pale Rider (1985) was primarily filmed in the Boulder Mountains and the Sawtooth National Recreation Area in central Idaho, just north of Sun Valley.