Ontario, Canada has awesome shipwrecks, very well preserved due to the cold fresh water. One of my favourites is the Wexford (70 feet) in Lake Huron. It is steel, fully intact and about 250 feet long by 40 feet wide and three decks high. It is an absolute playground outside and inside with more than you can see in one or two dives.
The Niagara II (100'), Forest City (150") and Arabia (105") in Tobermory, Ontario are amazing too, and the best in the area.
Lake Ontario in Kingston has beautiful shipwrecks like the Sheboygan, Katie Eccles, Marsh, Comet, and tonnes more (most around 100").
The St. Lawrence river out of Brockville, Ontario has great shipwrecks and warmer water (up to 75F in the summer with no thermocline). The Kinghorn (75") is probably the nicest on the Canadian side and the Keystorm (120") and Vickery (130") are really nice on the U.S. side.
All of the above were natural shipwrecks, some with many lives lost, some with none. All are very well preserved since they are not in salt water and deep enough to not be as affected by surface conditions.
The Spiegel Grove (120 or so) and Duane (120 or so) off Key Largo, Florida are amazing, and of course are in much warmer water.
Those are my favourites so far. Hope you get to do them sometime...