Lewis and Clark County

Also known as Lewis and Clark County, Montana, Lewis and Clark County, MT

county in Montana, United States

Key facts

Country: United States
State: Montana
Founded: June 2, 1865
Named after: Meriwether Lewis and William Clark
Seat: Helena
Largest city: Helena
Total: 3,498 sq mi (9,060 km )
Land: 3,459 sq mi (8,960 km )
Water: 39 sq mi (100 km ) 1.1%
Estimate 2025: 75,331
Density: 21.8/sq mi (8.4/km )
Time zone: UTC−7 ( Mountain )
Summer dst

Article

Lewis and Clark County is a county located in the U.S. state of Montana. As of the 2020 census, the population was 70,973. Its county seat and most populous city is Helena, the state capital. The numerical designation for Lewis and Clark County (used in the issuance of the state's license plates) is 5. The county was established on June 2, 1865, as one of the nine original counties of the Territory of Montana named Edgerton County in honor of Sidney Edgerton, first Governor of the Territory of Montana, and was renamed Lewis and Clark County on March 1, 1868, in honor of explorers Meriwether Lewis and William Clark. Lewis and Clark County is part of the Helena, Montana Micropolitan Statistical Area, and comprises the entirety of the Helena media market.

Geography