Greenwell is a 596-acre State Park located on the Patuxent River in St. Mary's County, Maryland. In 1971, John Phillip Greenwell, Jr. and his sister, Mary Wallace Greenwell, donated their 166.6 acre farm to the State of Maryland for use as a public park for everyone. The state subsequently purchased the adjacent 430-acre Bond property and joined the two to form the existing park. The park is managed in partnership with The Greenwell Foundation, a non-profit organization dedicated to providing outdoor accessible recreation.