Milford Square is a census-designated place in Milford Township, Bucks County, Pennsylvania. It is located along PA Route 663 near the borough of Trumbauersville. As of the 2010 census, the population was 897 residents. It is located on the Unami Creek (also called Swamp Creek) which drains into the Perkiomen Creek. It was known as Heistville after the Heist family who operated Achey's Mill and built a mill house next to it until c. 1850.Campbell's Bridge was listed on the National Register of Historic Places in 1988.It is also home to Achey's Bridge, the first concrete-reinforced bridge in America. Following the design of Henry Mercer. The bridge now sits on private property.