History Ada County was created by the Idaho Territory legislature on December 22, 1864, partitioned from Boise County. It is named for Ada Riggs, the daughter of H. C. Riggs, a member of the legislature; he established the county and was a co-founder of Boise. Canyon County, which originally included Payette County and most of Gem County, was partitioned from western Ada County in 1891.
history ada county was created by the idaho territory legislature on december 22 1864 partitioned from boise county it is named for ada riggs the daughter of h c riggs a member of the legislature; he established the county and was a co-founder of boise canyon county which originally included payette county and most of gem county was partitioned from western ada county in 1891