Old Swedes' Church, formally Holy Trinity Church, was built in 1698 by Swedish Lutheran settlers and consecrated on Trinity Sunday, June 4, 1699, making it one of the oldest church buildings in the United States still standing largely as originally constructed and in continuous use for worship. The congregation left Swedish Lutheranism and formally joined the Episcopal Church in 1791; it is today part of Trinity Episcopal Parish in the Episcopal Diocese of Delaware. The building was designated a National Historic Landmark in 1961.