Rush-Bagot.

This is coolbert:

Grave American violations of the Rush–Bagot Treaty? The Great Lakes of North America and border between Canada and the United States a demilitarized zone, military vessels limited both with regard to burden [tonnage] and armaments.

"The Rush–Bagot Treaty or Rush–Bagot Disarmament was a treaty between the United States and Great Britain limiting naval armaments on the Great Lakes and Lake Champlain, following the War of 1812. It was ratified by the United States Senate on April 16, 1818, and was confirmed by Canada, following Confederation in 1867."

"The treaty provided for a large demilitarization of lakes along the international boundary, where many British naval arrangements and forts remained. The treaty stipulated that the United States and British North America could each maintain one military vessel (no more than 100 tons burden) as well as one cannon (no more than eighteen pounds) on Lake Ontario and Lake Champlain. The remaining Great Lakes permitted the United States and British North America to keep two military vessels 'of like burden' on the waters armed with 'like force'."

American gunboat USS Wilmette during the period of the Great War stationed on the Great Lakes. Wilmette of a size and armaments greater than stipulated in the Rush-Bagot treaty of one hundred years earlier. 

USS Wilmette during training exercise actually firing weaponry at a captured German submarine in the aftermath of WW1 some period after hostilities having ended. This was the sinking of UC-97.

"A clause of the armistice treaty required all German combat vessels held by Allied forces to be destroyed before 1 July 1921. All armament, propulsion machinery, and navigation gear were removed from UC-97 before she was towed out into Lake Michigan by USS Hawk (IX-14) for use as a target during the annual summer training of naval reservists living in the Midwestern United States. USS Wilmette fired 18 rounds from a 4 in (10 cm) gun in 15 minutes to sink UC-97 20 nautical miles (37 km) off the coast of Highland Park, Illinois on 7 June 1921."

And yes, the American gunboat IX-29 the converted excursion vessel SS Eastland prior to WW1 capsizing with horrific loss of life the Chicago river.

coolbert.