St. Martin is a census-designated place (CDP) in Jackson County, Mississippi, United States. It is part of the Pascagoula Metropolitan Statistical Area. The population was 7,730 at the 2010 census, up from 6,676 at the 2000 census.
St. Martin is located along the Mississippi Gulf Coast at 30°26′31″N 88°52′13″W / 30.44194°N 88.87028°W / 30.44194; -88.87028 (30.441847, -88.870402). It is south of Interstate 10 and is bordered by the CDP of Gulf Hills to the east, Biloxi Bay to the south, and the city of D’Iberville to the west.
According to the United States Census Bureau, the CDP has a total area of 5.1 square miles (13.2 km), of which 4.2 square miles (11.0 km) are land and 0.85 square miles (2.2 km), or 16.84%, are water. St. Martin has either Biloxi or Ocean Springs mailing addresses. The ZIP codes are either 39532 or 39564.
As of the census of 2000, there were 6,676 people, 2,387 households, and 1,833 families residing in the CDP. The population density was 1,528.0 people per square mile (589.8/km²). There were 2,534 housing units at an average density of 580.0/sq mi (223.9/km²). The racial makeup of the CDP was 82.70% White, 7.94% African American, 0.52% Native American, 6.95% Asian, 0.07% Pacific Islander, 0.42% from other races, and 1.39% from two or more races. Hispanic or Latino of any race were 1.92% of the population.
There were 2,387 households, of which 36.5% had children under the age of 18 living with them, 56.6% were married couples living together, 14.7% had a female householder with no husband present, and 23.2% were non-families. 18.6% of all households were made up of individuals and 7.5% had someone living alone who was 65 years of age or older. The average household size was 2.80 and the average family size was 3.17.
In the CDP, the population was spread out with 27.3% under the age of 18, 8.7% from 18 to 24, 29.7% from 25 to 44, 23.8% from 45 to 64, and 10.5% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 96.6 males. For every 100 females age 18 and over, there were 94.1 males.
The median income for a household in the CDP was $41,167, and the median income for a family was $46,559. Males had a median income of $31,213 versus $22,958 for females. The per capita income for the CDP was $16,439. About 7.1% of families and 10.7% of the population were below the poverty line, including 14.0% of those under age 18 and 20.7% of those age 65 or over.