Lamar County is located in Southeastern Mississippi and is the second fastest growing county in the state. Lamar County was founded in 1904 and named after Supreme Court Justice Lucius Quintus Cincinnatus Lamar. As of the 2019 US Census, Lamar County has a population of 63,343. The cities of Hattiesburg, Lumberton, Purvis and Sumrall are all located within the county. The county seat is located in the city of Purvis.