Marion County area

Population and density of Marion County

The Census Bureau estimates that 992,196 people lived in Marion County on July 1, 2025. That ranks #52 of 3,222 county equivalents nationally and #1 of 92 in Indiana. Since the April 1, 2020 estimates base of 977,202, the population has grown by 14,994 (+1.5%), compared with +2.8% for Indiana as a whole.

With 396 square miles of land, that is 2,506 people per square mile (967 per km²), placing Marion County #58 nationally for density and #1 in Indiana. The median county equivalent has 47 people per square mile; the Indiana median is 88. Put another way, there are about 0.255 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 Marion County

16 incorporated places lie at least partly in Marion County. Together they are home to 992,196 people (100%); the other 0 (0%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Indianapolis city (balance), with 901,116 residents in the county. Among places with at least 1,000 residents in 2020, Speedway town grew fastest since then (+2.9%).

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

Metropolitan area

Marion County is a central county of the Indianapolis-Carmel-Greenwood, IN Metropolitan Statistical Area. Its 11 county equivalents have 2,205,695 residents on 4,086 square miles of land; Marion County accounts for 9.7% of the land and 45% of the residents. By combined land it ranks #71 of 393 metropolitan areas, and #33 by population. It belongs to the Indianapolis-Carmel-Muncie, IN Combined Statistical Area.

ZIP codes

41 ZIP Code Tabulation Areas have land in Marion County; 36 of them have most of their land inside the county, and the others mainly cover neighboring areas.

4607746107461134616346183462014620246203462044620546206462084621446216462174621846219462204622146222462244622546226462274622846229462314623446235462364623746239462404624146250462544625646259462604626846278

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 Marion County

Marion County shares a land border with 7 county equivalents. It has more land than 3 of them. The largest neighbor is Boone County (422.9 mi²) and the smallest is Hancock County (306 mi²). Together with its neighbors, Marion County forms a block of 3,061.5 mi² of land, of which it holds 12.9%.

How big is Marion County compared with U.S. states?

Marion County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 2.6 times as much. Indiana’s county land could hold about 90 areas the size of Marion County.

Another way to picture it: the same land area would fill a square about 19.9 miles (32 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 Marion County?

Marion County has more land than 678 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 Marion County at #2,588 nationally by total area, 44 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 1.7%, compared with a national county-equivalent median of 1.2% — 0.6 percentage points higher. 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 Marion 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.