Created on February 9, 1796, from part of Washington County and named for General Nathanael Greene. Waynesburg, the county seat, named for Major General Anthony Wayne, was laid out in 1796 and incorporated as a borough on January 29, 1816.

     First permanent settlement is believed to have been the Swan-VanMeter-Hughes party from Virginia, in 1767. Once the Indian hostility and Whiskey Rebellion problems had passed, this county was formed in order to benefit small farmers. Beginning with the Merino Sheep bonanza of the 1820s, wool became a major product. Although overshadowed by production elsewhere in the world, Greene still leads other Pennsylvania counties in sheep (occasionally challenged by Washington County). When the Monongahela River slackwater system reached Rice’s Landing in 1857, it became easier to market products. Bituminous coal mining began in 1902; in recent years this been Pennsylvania’s highest producing county, nearly all from subsurface mines. Natural gas was also found in abundance. Forty percent of the land is in farms, although cash receipts from agriculture are low. The tradition that it rains somewhere in the county every July 29 is a popular myth begun by a local pharmacist. Home of Governor Edward Martin.