The waterfall is 188 feet (57 m) high.

 

Taken October 15, 10:38 a.m.

1/1000 s, f/4.5, ISO 100

This photo was taken from the walkway to the Observation Tower that provides access to the Maid of the Mist tour boat. If you just want to go to the Observation Tower without going on the boat, you can do that for a minimal charge, although that may not be obvious. In my opinion, that walkway provides a better angle on American Falls than overlooks on land.

While it's common to use long exposures with waterfalls, this is a case where I think a really short exposure is worthwhile to show the texture of the water.