Ada, a S. W. county of Idaho, separated from Oregon by the Snake river (here also called the Saptin); area, about 2,800 sq. m.; pop. in 1870, 2,675. The county was organized in 1864. Mining is the principal occupation of the people. The total value of property in 1869 was $1,014,185. There are three newspapers. Capital, Boise City, which is also the capital of the territory.