Pine Bluff is the tenth-most populous city in the US state of Arkansas and the county seat of Jefferson County. It is the principal city of the Pine …Pine Bluff is the tenth-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.