From Ancestry.com Wiki
Hamden is a town in New Haven county in Connecticut. It was formed in 1786 from the following town or towns: New Haven. Hamden is a part of the Hamden probate district and has been since 1945. New Haven was/were the previous chronological district or districts. For more information, contact the county at Memorial Town Hall 2372 Whitney Ave. Hamden 06518-3207. On the attached map, New Haven is located at D5.
For information about the state of Connecticut see Connecticut Family History Research.