Chartered March 18, 1907, the American Federation of Musicians, Local 21, Inc. is the local union of the American Federation of Musicians of the United States and Canada for Delaware and parts of Pennsylvania, Maryland and Virginia. The AFM is the world's largest union of performing artists.

The territorial jurisdiction of Local 21 is the State of Delaware, its three counties, New Castle, Kent, and Sussex, and all its municipalities, towns and unincorporated areas. In Maryland, all of the following counties: Cecil, Kent, Queen Anne's, Talbot, Dorchester, Wicomico, Somerset, and Worcester including Ocean City. In Virginia, all of Accomac and Northampton counties. In Chester County, Pennsylvania, the following townships: Pocopson, East Marlboro, Pennsbury, Kennett Square, Kennett and New Garden. Also, Chester, PA, east eight miles, north to Delaware County line, south to Delaware River and the following in Chester County: Coatesville, South Coatesville, West Caln Twp., West Bradford, Newlin, East Fallowfield, Sadsbury, West Sadsbury, Atglen, Valley, Paperville, Parksburg, Highland, West Fallowfield, Londonderry, West Marlboro, Upper Oxford, Lower Oxford, Penn West Grove, London Grove, Avondale, Oxford, East Nottingham, West Nottingham, Elk, New London, Franklin, London, Britain, West Whiteland, Downingtown, East Whiteland, West Goshen, Malvern, Willistown, East Town, West Chester, Westtown, Thornbury, East Bradford and Birmingham. Also the establishment known as the RedFox Inn, in new Garden Twp.