San Sebastián Municipio area

Population and density of San Sebastián Municipio

The Census Bureau estimates that 39,019 people lived in San Sebastián Municipio on July 1, 2025. That ranks #1,231 of 3,222 county equivalents nationally and #23 of 78 in Puerto Rico. Since the April 1, 2020 estimates base of 39,345, the population has declined by 326 (−0.8%), compared with −3.1% for Puerto Rico as a whole.

With 70.5 square miles of land, that is 554 people per square mile (214 per km²), placing San Sebastián Municipio #314 nationally for density and #55 in Puerto Rico. The median county equivalent has 47 people per square mile; the Puerto Rico median is 754. Put another way, there are about 1.2 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 San Sebastián Municipio

Puerto Rico has no incorporated places below the municipio: San Sebastián Municipio is itself the local government. The Census Bureau describes the settlements inside it, such as zonas urbanas and comunidades, as statistical places, and publishes no separate annual estimates for them.

Metropolitan area

San Sebastián Municipio is a central county of the Aguadilla, PR Metropolitan Statistical Area. Its 7 county equivalents have 250,088 residents on 297.1 square miles of land; San Sebastián Municipio accounts for 23.7% of the land and 15.6% of the residents. By combined land it ranks #387 of 393 metropolitan areas, and #199 by population. It belongs to the Mayagüez-Aguadilla, PR Combined Statistical Area.

ZIP codes

3 ZIP Code Tabulation Areas have land in San Sebastián Municipio; 1 of them have most of their land inside the county, and the others mainly cover neighboring areas.

006690067800685

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 San Sebastián Municipio

San Sebastián Municipio shares a land border with 7 county equivalents. It has more land than every one of them. The largest neighbor is Lares Municipio (61.4 mi²) and the smallest is Quebradillas Municipio (22.7 mi²). Together with its neighbors, San Sebastián Municipio forms a block of 392.3 mi² of land, of which it holds 18%.

How big is San Sebastián Municipio compared with U.S. states?

San Sebastián Municipio has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 15 times as much. Puerto Rico’s county land could hold about 49 areas the size of San Sebastián Municipio.

Another way to picture it: the same land area would fill a square about 8.39 miles (13.5 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 San Sebastián Municipio?

San Sebastián Municipio has more land than 121 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 San Sebastián Municipio at #3,129 nationally by total area, 28 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 1.2%, 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 San Sebastián Municipio 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.