Following the Revolutionary War, an inn was built along a wagon trail (today's East Pittsburgh Street) that stretched from Philadelphia west over the Appalachian Mountains to Fort Pitt, now Pittsburgh. A tiny settlement known as Newtown grew around the inn, today the intersection of Pittsburgh and Main Streets.A raid by Guyasuta-led Seneca Indians accompanied by Canadian rangers burned Hannastown, the original Westmoreland County Seat north of Greensburg, in 1782. Newtown became the new county seat in 1785. In 1786 the county built a log courthouse on land purchased from two residents, Christopher Truby and William Jack. Every Westmoreland County Courthouse since has stood on this site. The area surrounding the courthouse became the original borough of Greensburg, named for Revolutionary War General Nathaniel Greene and formally incorporated as a Borough in 1799.

In the 1970's, as shopping malls and new shopping centers appeared outside the City, Greensburg's downtown was adversely affected as large downtown stores closed. However, the City became a center for service industries, professional offices and banking. Today, small downtown shops and a growing number of restaurants are reviving downtown as a mercantile center. Larger shopping centers can be found at the edges of the City.Light to moderate industry and service industries thrive in Greensburg. The City's lack of heavy industry has advantages. Economic downturns affect the community less than they do communities depending on one major industry. Housing growth continues on the northern end of the City, with the Saybrook Village and Evergreen Hill plans.Public education in Greensburg is handled by the Greensburg-Salem School District. The Diocese of Greensburg also maintains an elementary and secondary educational system and a number of private trade schools also exist in the City.