Greensburg is a town in and the parish seat of St. Helena Parish, Louisiana, United States. The population was 718 at the 2010 census. It is part of the Baton Rouge Metropolitan Statistical Area.Greensburg is one of the oldest towns in Louisiana. It has two 19th-century properties listed on the National Register of Historic Places, the old land office and the old parish jail.During the American Civil War, Union General Albert Lindley Lee left Baton Rouge with a division of cavalry on October 5, 1864, and raided Greensburg, where his men destroyed a tannery containing two thousand sides of leather. He also seized a large supply of quinine.