Gunboat "Philadelphia", by Dorwin, Harold, , Smithsonian Archives - History Div, Image of the Gunboat "Philadelphia" on display in the National Museum of American History. The American gunboat "Philadelphia" sank into Lake Champlain in October 1776, during a naval battle against the British in the American Revolution. Visible is the 12 pounder gun mounted at the bow. She was raised in 1935 with much of its equipment intact and came to the Museum in 1964, complete with the 24-pound ball that sent the gunboat to the bottom..