Marion County is a county of the U.S. state of Alabama. As of the 2020 census the population was 29,341. The county seat is Hamilton. The county was created by an act of the Alabama Territorial General Assembly on February 13, 1818. The county seat was originally established in Pikeville in 1820, and moved to Hamilton in 1881. The county was na…Marion County is a county of the U.S. state of Alabama. As of the 2020 census the population was 29,341. The county seat is Hamilton. The county was created by an act of the Alabama Territorial General Assembly on February 13, 1818. The county seat was originally established in Pikeville in 1820, and moved to Hamilton in 1881. The county was named by planter and US Indian agent John Dabney Terrell, Sr., in recognition of General Francis Marion of South Carolina.