Greensburg is a city in Decatur County, Indiana, United States. The population was counted at 11,492 at the 2010 census. The city is the county seat of Decatur County.HistoryGreensburg was laid out in 1822. The founder's wife being a native of Greensburg, Pennsylvania caused the name to be selected.The first post office at Greensburg opened in 1823, but the name of the post office was spelled Greensburgh until 1894.At the beginning of the twentieth century, race relations in Greensburg worsened, leading to the expulsion of African Americans from the city after race riots against them in 1906 and 1907. According to James W. Loewen, Greensburg then was for decades a sundown town, a town that was purposely all-white.The Bromwell Wire Works, Decatur County Courthouse, Greensburg Carnegie Public Library, Greensburg Downtown Historic District, Bright B. Harris House, Jerman School, and Knights of Pythias Building and Theatre are listed on the National Register of Historic Places.