Kootenai County is located in the U.S. state of Idaho. In 2018, the United States Census Bureau estimated the county's population at 161,505, making it the third-most populous county in Idaho and by far the largest in North Idaho, the county accounting for 45.4% of the region's total population. The county seat and largest city is Coeur d'Alene. The county was established in 1864 and named after the Kootenai tribe.