Okanogan County is a county located in the U.S. state of Washington along the Canada–U.S. border. As of the 2020 census, the population was 42,104. The county seat is Okanogan, while the largest city is Omak. Its area is the largest in the state. About a fifth of the county's residents live in the Greater Omak Area. The county forms a portion of the Okanogan Country. The first county seat was Ruby, which has now been a ghost town for more than 100 years.