As of the census2 of 2000, there are 21,216 people, 6,992 households, and 5,551 families residing in the parish. The population density is 33/km2 (86/mi2). There are 7,605 housing units at an average density of 12/km2 (31/mi2). The racial makeup of the parish is 49.99% White, 49.38% Black or African American, 0.09% Native American, 0.05% Asian, 0.00% Pacific Islander, 0.12% from other races, and 0.37% from two or more races. 0.61% of the population are Hispanic or Latino of any race.
There are 6,992 households out of which 38.90% have children under the age of 18 living with them, 55.30% are married couples living together, 19.30% have a female householder with no husband present, and 20.60% are non-families. 18.40% of all households are made up of individuals and 7.70% have someone living alone who is 65 years of age or older. The average household size is 3.00 and the average family size is 3.43.
In the parish the population is spread out with 29.50% under the age of 18, 9.80% from 18 to 24, 28.10% from 25 to 44, 21.40% from 45 to 64, and 11.10% who are 65 years of age or older. The median age is 34 years. For every 100 females there are 93.10 males. For every 100 females age 18 and over, there are 89.40 males.
The median income for a household in the parish is $35,277, and the median income for a family is $41,751. Males have a median income of $37,487 versus $21,712 for females. The per capita income for the parish is $14,381. 20.70% of the population and 18.00% of families are below the poverty line. Out of the total people living in poverty, 27.70% are under the age of 18 and 15.10% are 65 or older.
St. James is one of the state's nineteen original parishes, created by act of the territorial legislature, March 31, 1807. The original seat of government was the community of St. James, on the west bank of the Mississippi, but this was moved in 1869 to what is now Convent, on the east bank. St. James is the only cultivation site in the world for perique tobacco, introduced by an Acadian exile, Pierre Chenet, whose nickname was "Perique." It has been produced by his descendants for nearly two centuries (now covering only a 300-acre tract) and is in great demand by large tobacco companies.