George Brown's Sons Cotton and Woolen Mill, now known as Sassafras Alley Apartments, is a historic mill complex located at Mount Joy, Lancaster County, Pennsylvania. The complex includes nine contributing buildings. They are identified as Building A through Building I, and date from the early 19th century to 1916. The buildings were converted to apartments in 1988–1991. It was listed on the National Register of Historic Places in 1995.