The Thornton unit comprises 2,080 acres located about eight miles northeast of Prosser on the west side of Benton County, and about three miles southwest of the Rattlesnake Slope unit. It was acquired by WDFW in 1996 for mule deer, upland birds, transitory elk (the Rattlesnake Hills herd), sage grouse, and other shrub-steppe obligate species. By 1999 all 1,300 acres of croplands had been converted to native-like grasslands. Thornton supports long ridges of shrub steppe, intermixed with the former wheat fields. Future activities on this site may include the development of small check structures within the drainages to collect spring runoff. This will help maintain available water for wildlife and support more riparian vegetation. Currently, most intermittent water disappears by mid-summer. Snipes Creek bisects the unit and provides limited but important riparian habitat in places. A spring in the center of this unit provides free water nearly year round and other, smaller springs exist in other canyons. The unit is a popular hunting area for deer and elk. Historically, chukar hunting was common but populations have waned in recent years. The unit has two access sites, one along Rothrock Road on the west side and a new one along Case Road on the east side that compensates for the closure of Sharp Road.