Of 44 counties in the Gem State, Ada County is 31st in terms of its size (1,060 square miles). Ada County is in Southwestern Idaho. Recent Land Network data totals nearly 1,000 acres of riverfront land for sale in Idaho's Ada County, which is valued at a combined $5 million. Browse all waterfront property for sale in Ada County on the Land Network to find the marina, lakefront and other recreational property that meets your needs, from waterside land perfect as a retirement investment to existing residential waterfront land and property for hunting, fishing and other outdoor-recreation pursuits! The most common type of land for sale by combined acreage in Ada County is residential property.