St. Tammany Parish area

Population and density of St. Tammany Parish

The Census Bureau estimates that 279,108 people lived in St. Tammany Parish on July 1, 2025. That ranks #263 of 3,222 county equivalents nationally and #4 of 64 in Louisiana. Since the April 1, 2020 estimates base of 264,565, the population has grown by 14,543 (+5.5%), compared with −0.9% for Louisiana as a whole.

With 845.3 square miles of land, that is 330 people per square mile (127 per km²), placing St. Tammany Parish #472 nationally for density and #6 in Louisiana. The median county equivalent has 47 people per square mile; the Louisiana median is 48. Put another way, there are about 1.9 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 St. Tammany Parish

8 incorporated places lie at least partly in St. Tammany Parish. Together they are home to 60,572 people (21.7%); the other 218,536 (78.3%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Slidell city, with 28,341 residents in the county. The county seat, Covington city, has 11,721 residents. Among places with at least 1,000 residents in 2020, Pearl River town grew fastest since then (+6.6%).

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

Metropolitan area

St. Tammany Parish is a central county of the Slidell-Mandeville-Covington, LA Metropolitan Statistical Area. St. Tammany Parish is the area’s only county equivalent, so the metro area has the same 845.3 square miles of land. By combined land it ranks #301 of 393 metropolitan areas, and #185 by population. It belongs to the New Orleans-Metairie-Slidell, LA-MS Combined Statistical Area.

ZIP codes

18 ZIP Code Tabulation Areas have land in St. Tammany Parish; 16 of them have most of their land inside the county, and the others mainly cover neighboring areas.

704207042770431704337043570437704387044570447704487045270457704587046070461704637046470471

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 St. Tammany Parish

St. Tammany Parish shares a land border with 7 county equivalents, including 2 in Mississippi. It has more land than every one of them. The largest neighbor is Pearl River County (811.5 mi²) and the smallest is Orleans Parish (169.6 mi²). Together with its neighbors, St. Tammany Parish forms a block of 4,276.5 mi² of land, of which it holds 19.8%.

How big is St. Tammany Parish compared with U.S. states?

St. Tammany Parish has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.2 times as much. Louisiana’s county land could hold about 51 areas the size of St. Tammany Parish.

Another way to picture it: the same land area would fill a square about 29.1 miles (46.8 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 St. Tammany Parish?

St. Tammany Parish has more land than 2,234 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 St. Tammany Parish at #669 nationally by total area, 319 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 22.8%, compared with a national county-equivalent median of 1.2% — 21.7 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 St. Tammany 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.