Pine Bluff is the 10th most populous city in the US state of Arkansas and the county seat of Jefferson County. It is the principal city of the Pine Bluff Metropolitan Statistical Area and part of the Little Rock-North Little Rock-Pine Bluff Combined Statistical Area. The population of the city was 41,253 in the 2020 census. The city is situated in the Southeast section of the Arkansas Delta and straddles the Arkansas Timberlands region to its west. Its topography is flat with wide expanses of farmland, similar to other places in the Delta Lowlands. Pine Bluff has numerous creeks, streams, and bayous, including Bayou Bartholomew, the longest bayou in the world and the second most ecologically diverse stream in the United States. Large bodies of water include Lake Pine Bluff, Lake Langhofer (Slack Water Harbor), and the Arkansas River.