The Sedgwick Collection at New Haven Colony Historical Society
Full catalog of this immense collection, plus a history of Sedgwick Genealological Research.
The Massachusetts Historical Society Library
A very large Sedgwick Family collection relating largely to Theodore Sedgwick (1746 - 1813) and his descendants. Search for Sedgwick at their "Abigail" search engine
Calvert County (Maryland) Historical Society
Family Collections for (Thomas) Sedwick and several related families.
Buy and read History of Calvert County Maryland by Charles Stein immediately!
The State Historical Society of Wisconsin
Not a specific Sedgwick collection, but they have a lot of Sedgwick materials
Go to the Library or Archives sections and search
You can make better. Send your data.