Lewis and Clark County area

Population and density of Lewis and Clark County

The Census Bureau estimates that 75,331 people lived in Lewis and Clark County on July 1, 2025. That ranks #758 of 3,222 county equivalents nationally and #6 of 56 in Montana. Since the April 1, 2020 estimates base of 70,971, the population has grown by 4,360 (+6.1%), compared with +5.6% for Montana as a whole.

With 3,458.4 square miles of land, that is 22 people per square mile (8.4 per km²), placing Lewis and Clark County #2,263 nationally for density and #8 in Montana. The median county equivalent has 47 people per square mile; the Montana median is 2.8. Put another way, there are about 29 acres of land per resident.

U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.

Cities and towns in Lewis and Clark County

2 incorporated places lie at least partly in Lewis and Clark County. Together they are home to 37,463 people (49.7%); the other 37,868 (50.3%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Helena city, with 35,138 residents in the county. Among places with at least 1,000 residents in 2020, East Helena city grew fastest since then (+20%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Lewis and Clark County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.

Metropolitan area

Lewis and Clark County is a central county of the Helena, MT Metropolitan Statistical Area. Its 3 county equivalents have 97,153 residents on 6,307.7 square miles of land; Lewis and Clark County accounts for 54.8% of the land and 77.5% of the residents. By combined land it ranks #30 of 393 metropolitan areas, and #374 by population.

ZIP codes

12 ZIP Code Tabulation Areas have land in Lewis and Clark County; 10 of them have most of their land inside the county, and the others mainly cover neighboring areas.

594105942159601596025962359625596335963559636596395964059648

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering Lewis and Clark County

Lewis and Clark County shares a land border with 7 county equivalents. It has more land than 6 of them. The largest neighbor is Flathead County (5,087.3 mi²) and the smallest is Broadwater County (1,192.4 mi²). Together with its neighbors, Lewis and Clark County forms a block of 21,082.8 mi² of land, of which it holds 16.4%.

How big is Lewis and Clark County compared with U.S. states?

Lewis and Clark County has more land than 2 of the 50 states. It is about 1.8 times the land area of Delaware (1,948.6 mi²), while Connecticut, the next larger state, has 1.4 times as much land (4,842.5 mi²). Montana’s county land could hold about 42 areas the size of Lewis and Clark County.

Another way to picture it: the same land area would fill a square about 58.8 miles (94.6 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.

State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.

What stands out about Lewis and Clark County?

Lewis and Clark County has more land than 3,077 of the other 3,221 county equivalents in the dataset.

A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.

Does including water change its rank?

Using land plus water places Lewis and Clark County at #154 nationally by total area, 9 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.

Its water share is 1.1%, compared with a national county-equivalent median of 1.2%. The two percentages are within 0.1 percentage points of each other. This describes the statistical geography’s land/water mix, not flood exposure or developable land.

Closest positions in the national land ranking

These entries sit immediately beside Lewis and Clark County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.