Ada County is located in the southwestern part of Idaho, United States. As of the 2020 census, the county had a population of 494,967, which by 2022 was estimated to have risen to 518,907. Ada County is by far the state's most populous county; it is home to 26.8% of the state's population. The county seat and largest city is Boise, which is also the state capital. Ada County is included in the Boise metropolitan area. The Ada County Highway District has jurisdiction over all the local county and city streets, except for private roads and state roads. In the interior Pacific Northwest east of the Cascade Range, Ada County ranks second in population, behind Spokane County, Washington.
James A. McClure Federal Building and U.S. Courthouse in Boise, Idaho.
Southwestern Idaho is a geographical term for the area along the U.S. state of Idaho's borders with Oregon and Nevada. It includes the populous areas of the Boise metropolitan area and the Treasure Valley.
A historic building in Silver City, a ghost town located in Southwestern Idaho.
Women riding in a rig in Boise, Idaho, 1910.
Cherry orchards, farm land, and irrigation located in Emmett, Idaho. This photo was taken in July 1941.
