Full of detailed information about local maritime matters, as well as custodian of several interesting naval and commercial vessels (open for tours from mid-May to mid-October), including the tugboat USAT LT-5 Major Elisha K Henson that saw action during the Normandy landings of WWII.
The museum restored the historic Oswego West Pierhead Lighthouse in 2013, which you can see at the end of the breakwater jutting into Lake Ontario.