Westmoreland County is a county located in the U.S. state of Pennsylvania. It was founded on February 26, 1773, and was the first county in the colony of Pennsylvania west of the Allegheny Mountains. Westmoreland County originally included the present-day counties of Fayette, Washington, Greene, and parts of Beaver, Allegheny, Indiana, and Armstrong counties. At the 2000 census, the population was 369,993. The county seat is Greensburg. It is wholly part of the Pittsburgh Metro Area, while north-eastern Westmoreland County borders the Johnstown Metro Area. A major coal strike occurred in the county in the winter of 1910–11.