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.

Founded: December 22, 1864
Named for: Ada Riggs
Seat: Boise
Largest city: Boise
Total: 1,060 sq mi (2,745.39 km²)
Land: 1,053 sq mi (2,727.26 km²)
Water: 7.9 sq mi (20.46 km²), 0.7
Time zone: Mountain: UTC-7-6
Website: [www.adaweb.net]
Official Website: http://www.adaweb.net
Wikidata description: county in Idaho, United States
Wikidata id: Q109820
Wikidata label: Ada County
Wikidata aliases: Array
Source
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