Rock Lake is the deepest and largest of all scabland lakes left behind from the Missoula Floods, and holds that distinction for all of eastern Washington. At its deepest, it is more than deep, although the official measurement is uncertain. The lake is over long and averages in width, and is accessible via a solitary landing area located on the south end. The rest of the shoreline is inaccessible to vehicles, other than a few private properties. Located approximately south of Cheney, Rock Lake is in a moderately remote location. Other towns in the area include Sprague, St. John, and Rosalia, although all are a number of miles away. Rock Lake receives the majority of its water from Rock Creek, which is a tributary of the Palouse River, as well as Negro Creek.