||Jefferson Parish (French: Paroisse de Jefferson) is a parish in Louisiana, United States that includes most of the suburbs of New Orleans. The seat of parish government is Gretna.
According to the 2010 census, Jefferson had a population of 432,552. Metropolitan New Orleans, a seven-parish area which includes Jefferson, is the largest metropolitan area in the state. Jefferson Parish is considered part of the Greater New Orleans Area. Jefferson Parish was less affected by Hurricane Katrina in 2005 and has rebounded at a more rapid pace than neighboring Orleans Parish. A population estimate conducted in July 2007 by the Louisiana Recovery Authority put Jefferson at 440,339 residents, or 98% of its 2000 total, making it in 2007 the most populous parish in the state. As of the 2010 census, East Baton Rouge Parish is the most populous parish in Louisiana.
The parish has a total area of 642 square miles (1,662.8 km2), of which 307 square miles (795.1 km2) is land and 336 square miles (870.2 km2) (52.29%) is water.
With the exception of the island Grand Isle, the only roads leaving Jefferson parish go to St. Charles Parish on the west and both Orleans Parish and Plaquemines Parish on the east. Lake Pontchartrain is situated to the north of Jefferson Parish. The southern half of Jefferson parish is uninhabited marshland. Regarding Grand Isle, the only roads connecting it to the rest of Jefferson Parish run through Lafourche Parish and St. Charles Parish
As of the 2000 census, there were 455,466 people living in Jefferson Parish. There were 120,191 families residing in the parish. The population density was 1,486 people per square mile (574/km˛). There were 187,907 housing units at an average density of 613 per square mile (237/km˛). The racial makeup of the parish was 69.82% White, 22.86% Black or African American, 0.45% Native American, 3.09% Asian, 0.03% Pacific Islander, 2.03% from other races, and 1.72% from two or more races. 7.12% of the population were Hispanic or Latino of any race.
There were 176,234 households out of which 31.90% had children under the age of 18 living with them, 48.20% were married couples living together, 15.40% had a female householder with no husband present, and 31.80% were non-families. 26.70% of all households were made up of individuals and 8.40% had someone living alone who was 65 years of age or older. The average household size was 2.56 and the average family size was 3.13.
In the parish the population was spread out with 25.30% under the age of 18, 9.10% from 18 to 24, 30.20% from 25 to 44, 23.40% from 45 to 64, and 11.90% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 92.40 males. For every 100 females age 18 and over, there were 88.60 males.
The median income for a household in the parish was $38,435, and the median income for a family was $45,834. Males had a median income of $35,081 versus $24,921 for females. The per capita income for the parish was $19,953. About 10.80% of families and 13.70% of the population were below the poverty line, including 20.00% of those under age 18 and 9.80% of those age 65 or over.