Greensburg is a city in and the county seat of Westmoreland County, Pennsylvania, United States. The population was 14,976 at the 2020 …Greensburg is a city in and the county seat of Westmoreland County, Pennsylvania, United States. The population was 14,976 at the 2020 census. Located 30 miles southeast of Pittsburgh, Greensburg is a part of the Pittsburgh metropolitan area. The city lies within the Laurel Highlands and the ecoregion of the Western Allegheny Plateau. The city is named after Nathanael Greene, a major general of the Continental Army in the American Revolutionary War.