Simpsonville is an unincorporated community in Howard County, Maryland, United States.
People and nature have long flourished beside the Middle Patuxent River. Over 12,000 years ago, Native Americans hunted deer and gathered acorns and other wild food in the woods and waters. People from Woodland Indian cultures settled nearby about 2,000 years ago, leaving traces of their lives in the earthenware pottery and stone tools they left behind. In 1741, John Hobbs acquired the patent on the lands around Simpsonville. The land passed to Vachel Worthington in 1789, followed by Richard Owings in 1796.The early 19th century Simpsonville Mill water-powered grist mill and saw mill was built here, as well as a woolen factory, wheelwright shop, blacksmith shop, and nine houses. In 1850, the town became known as Simpsonville, named after its first postmaster, Charles Simpson. In 1852, Charles Ridgley Simpson bought 215 acres which included the mill and town center.