Its western border is formed by the Pearl River, an important transportation route in the 19th century.

[2] The county is named for Josiah Simpson (1787-1817),[3] a territorial judge who also served as a delegate to Mississippi's Constitutional Convention.

[4] Simpson County is part of the Jackson, MS Metropolitan Statistical Area.

[5] As of the 2020 United States census, there were 25,949 people, 9,486 households, and 6,617 families residing in the county.

[15] The district maintains the Simpson County Center.