Assumption Parish area

Population and density of Assumption Parish

The Census Bureau estimates that 19,720 people lived in Assumption Parish on July 1, 2025. That ranks #1,899 of 3,222 county equivalents nationally and #43 of 64 in Louisiana. Since the April 1, 2020 estimates base of 21,043, the population has declined by 1,323 (−6.3%), compared with −0.9% for Louisiana as a whole.

With 344 square miles of land, that is 57 people per square mile (22 per km²), placing Assumption Parish #1,427 nationally for density and #29 in Louisiana. The median county equivalent has 47 people per square mile; the Louisiana median is 48. Put another way, there are about 11 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 Assumption Parish

1 incorporated place lies at least partly in Assumption Parish. Together they are home to 500 people (2.5%); the other 19,220 (97.5%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Napoleonville village, with 500 residents in the county.

Metropolitan area

Assumption Parish is an outlying county of the Baton Rouge, LA Metropolitan Statistical Area. Its 10 county equivalents have 888,699 residents on 4,367.8 square miles of land; Assumption Parish accounts for 7.9% of the land and 2.2% of the residents. By combined land it ranks #61 of 393 metropolitan areas, and #68 by population. It belongs to the Baton Rouge-Hammond, LA Combined Statistical Area.

ZIP codes

9 ZIP Code Tabulation Areas have land in Assumption Parish; 6 of them have most of their land inside the county, and the others mainly cover neighboring areas.

703017033970341703467037270380703907039170393

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 Assumption Parish

Assumption Parish shares a land border with 8 county equivalents. It has more land than 2 of them. The largest neighbor is Terrebonne Parish (1,229.9 mi²) and the smallest is St. James Parish (237.9 mi²). Together with its neighbors, Assumption Parish forms a block of 5,659.6 mi² of land, of which it holds 6.1%.

How big is Assumption Parish compared with U.S. states?

Assumption Parish has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 3 times as much. Louisiana’s county land could hold about 126 areas the size of Assumption Parish.

Another way to picture it: the same land area would fill a square about 18.5 miles (29.8 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 Assumption Parish?

Assumption Parish has more land than 525 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 Assumption Parish at #2,689 nationally by total area, 8 places closer to the top than its land rank. The water assigned to this geography moves it ahead of some county equivalents with more land.

Its water share is 7%, compared with a national county-equivalent median of 1.2% — 5.8 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 Assumption Parish 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.