John Brown's Farm is the abolitionis's farmhouse and grave. It is in Lake Placid, near the ski jumps, and will certainly make you think about one of the more difficult times in our nation's history.
Fort Ticonderoga in Ticonderoga is very well preserved and well set up for visitors to understand what happened there. The British were there when the Americans just walked in one night and took it over. The cannons were moved to Boston and, in a bluff, caused the British to evacuate the city. It is quite a story. In the summer of 2010 they are having night-time ghost hunting tours!
Crown Point Historical Site - is in Crown Point just before you go over the bridge to Vermont. The French, the British and Americans all fought over this place.
Fort William Henry is in Lake George and it was a key site of the French and Indian Wars.