Both the 1995 map cited above and the new 2013 map of the U.S. Geological Survey most of the Horseshoe Falls is in Canada, and both U.S. and New York State boundaries are shown on the newer map.
Both the 1995 map cited above and the new 2013 map show approximately two-thirds is in Canada. Both U.S. and New York State boundaries are shown on the newer map.