The city is a popular tourist attraction with many old Spanish builidings, including the fortress Castillo de San Marcos. The fortress was occupied by Union troops during the American Civil War and later served as a prison for the Native American leader Cochise.
According to the United States Census Bureau, the city has a total area of 27.8 km² (10.7 mi²). 21.7 km² (8.4 mi²) of it is land and 6.1 km² (2.4 mi²) of it is water. The total area is 21.99% water.
As of the census of 2000, there are 11,592 people, 4,963 households, and 2,600 families residing in the city. The population density is 534.7/km² (1,384.6/mi²). There are 5,642 housing units at an average density of 260.3/km² (673.9/mi²). The racial makeup of the city is 81.21% White, 15.07% African American, 0.41% Native American, 0.72% Asian, 0.09% Pacific Islander, 0.88% from other races, and 1.61% from two or more races. 3.11% of the population are Hispanic or Latino of any race.
There are 4,963 households out of which 18.6% have children under the age of 18 living with them, 37.4% are married couples living together, 12.4% have a female householder with no husband present, and 47.6% are non-families. 36.7% of all households are made up of individuals and 14.5% have someone living alone who is 65 years of age or older. The average household size is 2.11 and the average family size is 2.76.
In the city the population is spread out with 16.1% under the age of 18, 15.3% from 18 to 24, 23.9% from 25 to 44, 25.2% from 45 to 64, and 19.5% who are 65 years of age or older. The median age is 42 years. For every 100 females there are 84.6 males. For every 100 females age 18 and over, there are 81.4 males.
The median income for a household in the city is $32,358, and the median income for a family is $41,892. Males have a median income of $27,099 versus $25,121 for females. The per capita income for the city is $21,225. 15.8% of the population and 9.8% of families are below the poverty line. Out of the total people living in poverty, 25.8% are under the age of 18 and 10.0% are 65 or older.