Old South Church in Boston, Massachusetts, (also known as New Old South Church or Third Church) is a historic United Church of Christ congregation first organized in 1669. Its present building was designed in the Gothic Revival style by Charles Amos Cummings and Willard T. Sears, completed in 1873, and amplified by the architects Allen & Collens between 1935–1937. The church, which was built on newly filled land in the Back Bay section of Boston, is located at 645 Boylston Street on Copley Square. It was designated a National Historic Landmark in 1970 for its architectural significance as one of the finest High Victorian Gothic churches in New England. It is home to one of the older religious communities in the United States.