Sedgefield is a town and civil parish in County Durham, England. It has a population of 4,534, increasing to 5,211 at the 2011 census.St Edmund's church in Sedgefield is noted for its ornate 17th century Cosin woodwork, unique to County Durham since the display in Brancepeth was destroyed in a fire.The 18th century saw the architect James Paine commissioned by John Burdon in 1754 to design and construct a Palladian estate at nearby Hardwick Hall.