Duncan Church, also known as Saint Placidus Catholic Church, is a historic church near Gann Valley, South Dakota. It is located southwest of Crow Creek, about 2 miles (3.2 km) south of the county line. It is about 13 miles (21 km) north and west of Gann Valley.[2] It was built in 1927 and was added to the National Register in 1999.[1]
It is a basilica plan church about 28 by 42 feet (8.5 m × 12.8 m) in size. It has clapboard siding and a gable roof.[2]