Benton County administrative offices are located at 620 Market Street, Prosser, WA 99350; phone: 509-786-5710.
Benton County  was named after Senator Thomas Hart Benton of Missouri. The county is located in the southeastern part of the state and is bordered on the south and east by the Columbia River.
Many famous explorers of the Northwest passed through Benton County, among them, Lewis and Clark and Captain Bonneville.
Early wagon roads from Walla Walla to Puget Sound also traversed the county. In the 1880s, the coming of railroads brought settlers to the region and the irrigation projects of the 1890s created a rich agricultural economy. The establishment of the Hanford Atomic Energy Center has made the county the nation's major atomic research center. The county enjoys a diversified economy based on agriculture, wood products, food production, government installations and is emerging as one of the leading wine centers of Washington State.