Hartford was established as a diocese on November 28, 1843 and created as an archdiocese on August 6, 1953. It includes the following towns and cities:

Ansonia, Avon, Bantam, Barkhamsted, Beacon Falls, Berlin, Bethany, Bethlehem, Bloomfield, Branford, Bridgewater, Bristol, Broad Brook, Canaan, Canton, Cheshire, Colebrook, Collinsville, Cornwall, Cornwall Bridge, Derby, Devon, East Berlin, East Granby, East Hartford, East Hartland, East Haven, East Windsor, Elmwood, Enfield, Farmington, Forestville, Glastonbury, Goshen, Granby, Guilford, Hamden, Hartford, Hartland, Harwinton, Kensington, Kent, Lakeville, Litchfield, Madison, Manchester, Marlborough, Meriden, Middlebury, Milford, Mount Carmel, Naugatuck, New Britain, New Hartford, New Haven, New Milford, New Preston, Newington, Norfolk, North Branford, North Canaan, North Haven, Northfield, Northford, Oakville, Orange, Oxford, Plainville, Plantsville, Pleasant Valley, Plymouth, Poquonock, Prospect, Rocky Hill, Roxbury, Salisbury, Seymour, Sharon, Simsbury, South Glastonbury, South Meriden, South Windsor, Southbury, Southington, Suffield, Tariffville, Terryville, Thomaston, Torrington, Union City, Unionville, Wallingford, Warren, Washington Depot, Waterbury, Watertown, West Hartford, West Haven, West Simsbury, Wethersfield, Winchester, Windsor, Windsor Locks, Winsted, Wolcott, Woodbridge, Woodbury, Woodmont, Yalesville.