Warren County is a county located in the U.S. state of Mississippi. Its western border is formed by the Mississippi River. As of the 2020 census, the population was 44,722. Its county seat is Vicksburg. Established by legislative act of December 22, 1809, Warren County is named for American Revolutionary War officer Joseph Warren. Part of the Mississippi Delta and the historic cotton culture, Warren County had major plantations. Vicksburg was an important river port.