Cameron County, Texas  Cameron County, officially the County of Cameron, is the southernmost county in the U.S. state of Texas. As of the 2010 census, its population was 406,220. Its county seat is Brownsville. The county was founded in 1848 and is named for Captain Ewen Cameron, a soldier during the Texas Revolution and in the ill-fated Mier Expedition. During the later 19th century and through World War II, Fort Brown was a US Army outpost here, stimulating the development of the city of Brownsville. Cameron County is part of the Brownsville–Harlingen, TX Metropolitan Statistical Area as well as the Brownsville–Harlingen–Raymondville, TX Combined Statistical Area, which itself is part of the larger Rio Grande Valley region. According to the U.S. Census Bureau, the county has a total area of , of which is land and (30%) is water. To the east, the county borders the Gulf of Mexico. As of the census of 2010, there were 406,220 people, 119,631 households, and 96,579 families residing in the county. The population density was 370 people per square mile (143/km2). There were 141,924 housing units at an average density of 132 per square mile (51/km2). The racial makeup of the county was 87.0% White, 0.5% Black or African American, 0.4% Native American, 0.7% Asian, 0.03% Pacific Islander, 9.8% from other races, and 1.5% from two or more races. 88.1% of the population were Hispanic or Latino of any race. There were 119,631 households, out of which 50.3% had children under the age of 18 living with them, 60.80% were married couples living together, 20.0% had a female householder with no husband present, and 19.3% were non-families. 16.40% of all households were made up of individuals, and 7.30% had someone living alone who was 65 years of age or older. The average household size was 3.36 and the average family size was 3.80. In the county, the population was spread out, with 33.0% under the age of 18, 9.7% from 18 to 24, 25.6% from 25 to 44, 20.6% from 45 to 64, and 11.10% who were 65 years of age or older.