The architectural surveys in the Connecticut Historic Preservation Collection are a tremendous source for those who are researching historic properties in the state, and one of our most regularly requested collections here in the archives. But there are several other ways to find information about historic properties, including:
The Historic American Buildings Survey at the Library of Congress: http://www.loc.gov/pictures/collection/hh/
The National Park Service’s National Register of Historic Places: http://nrhp.focus.nps.gov/natreghome.do?searchtype=natreghome
The Connecticut State Library’s database of 1930s WPA Architectural Surveys/Census of Old Buildings in Connecticut: http://cslib.cdmhost.com/cdm/landingpage/collection/p4005coll7
List of Historic National Landmarks in Connecticut: http://en.wikipedia.org/wiki/List_of_National_Historic_Landmarks_in_Connecticut
Let me know if you know of others so that I can add them to the list.