2020 census
As of the 2020 United States census, there were 22,169 people, 6,989 households, and 4,651 families residing in the parish.
2000 census
As of the census of 2000, there were 18,698 people, 7,073 households, and 5,276 families residing in the parish. The population density was 29 people per square mile (11/km2). There were 8,531 housing units at an average density of 13 per square mile (5/km2). The racial makeup of the parish was 85.43% White, 11.88% Black or African American, 0.89% Native American, 0.14% Asian, 0.03% Pacific Islander, 0.36% from other races, and 1.28% from two or more races. 1.14% of the population were Hispanic or Latino of any race.
The decreases in population from 1910 to 1920, and from 1940 to 1960, were chiefly caused by different phases of the Great Migration, as African Americans left segregation and oppression of the South to seek better opportunities in the North, during the first phase, and in the West, especially California's defense industry, in the second phase. Tens of thousands of migrants left Louisiana during times of agricultural difficulties and the collapse of agricultural labor after mechanization.
In 2000, there were 7,073 households, out of which 36.50% had children under the age of 18 living with them, 57.20% were married couples living together, 12.90% had a female householder with no husband present, and 25.40% were non-families. 22.60% of all households were made up of individuals, and 10.10% had someone living alone who was 65 years of age or older. The average household size was 2.61 and the average family size was 3.06.
In the parish the population was spread out, with 28.30% under the age of 18, 7.90% from 18 to 24, 28.10% from 25 to 44, 23.00% from 45 to 64, and 12.70% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 96.10 males. For every 100 females age 18 and over, there were 93.00 males.
The median income for a household in the parish was $29,622, and the median income for a family was $34,878. Males had a median income of $31,235 versus $20,470 for females. The per capita income for the parish was $14,410. About 16.90% of families and 21.50% of the population were below the poverty line, including 27.30% of those under age 18 and 16.20% of those age 65 or over.
Government and infrastructure
The Federal Bureau of Prisons U.S. Penitentiary, Pollock is located in an unincorporated area in the parish, near Pollock.
Education
Public schools in Grant Parish are operated by the Grant Parish School Board.
National Guard
A Company 199TH FSB (Forward Support Battalion) resides in Colfax, Louisiana. This unit deployed twice to Iraq as part of the 256TH IBCT in 2004-5 and 2010.
Communities
thumb|200px|Map of Grant Parish, with municipal labels
Towns
Colfax (parish seat and largest municipality)
Montgomery
Pollock
Villages
Creola
Dry Prong
Georgetown
Unincorporated areas
Census-designated places
Prospect
Rock Hill
Unincorporated communities
Aloha
Bentley
Fishville
Hargis
Oak Grove
Selma
Verda
Prison
Notable people
W. K. Brown, state representative from Grant Parish from 1960 to 1972
Joe T. Cawthorn (1911-1967), lawyer, businessman, and politician affiliated with the Long faction, born in Selma in Grant Parish, resided in Mansfield in DeSoto Parish
Billy Ray Chandler, state representative from Grant Parish, 2006-2012
Jesse C. Deen (1922-2015), state representative from primarily Bossier Parish, 1972–1988; reared in the Hargis Community near Montgomery
Stephen Lee "Steve" Gunn, former mayor of Montgomery; represented Grant Parish in the legislature as an Independent from 1992 to 1996
Leonard R. "Pop" Hataway, sheriff of Grant Parish, 1976 to 2008; member of the Louisiana Board of Pardons and Paroles; member of the Louisiana Political Museum and Hall of Fame
Ed Head (1918–1980), Major League Baseball player who played for the Brooklyn Dodgers
Swords Lee, timber owner from Pollock and Alexandria; former Grant Parish assessor and state representative
W. T. McCain (1913-1993) - State representative for Grant Parish 1940 to 1948; first state court judge for only Grant Parish (1976), lawyer in Colfax
W.L. Rambo, member of both houses of the Louisiana State Legislature from Georgetown.
Ed Tarpley (born 1953), district attorney for Grant Parish from 1991 to 1997
Richard S. Thompson (1916-1997), state representative from Grant Parish from 1972 to 1984
Russ Springer, Major League baseball player