Clark County

County in southeastern Nevada, USA; area 20,938 sq km/8,084 sq mi; population (1990) 741,500. The county is bordered by California to the west and Arizona to the east, and drained by the Colorado and Virginia rivers. Its seat is Las Vegas. It is by far the most populous county in the state; increasing suburbanization fuelled an over 60% rise in population in 1980–90. Though the county has magnesium and other mineral deposits and produces livestock, dairy goods, and vegetables, much of its economy is focused on Las Vegas's gambling and tourist industry. Also in Clark County is Hoover Dam, which forms Lake Mead in the east-central portion.

Clark County

County in west-central Ohio, USA; area 1,031 sq km/398 sq mi; population (1990) 147,500. The county is crossed by the Mad River and numerous other rivers and streams. The sizeable Clarence J Brown Reservoir is in the county. There is manufacturing at Springfield, the county seat. Otherwise the local economy depends on the exploitation of limestone, sand, and gravel as well as mixed farming (dairy, grain, and livestock).

Clark County

County in southwestern Washington, USA; area 1,624 sq km/627 sq mi; population (1990) 238,100. The county borders Oregon (along the Columbia River) on the south and west. Vancouver is its seat. Fruit, nuts, wool, and cheese are produced here, and along the Columbia shipping, pulp and paper milling and diversified manufactures are important. The county – part of the Portland, Oregon, metropolitan area – has doubled in population since 1970.