The lower part of the Tahquomonon Falls in the Upper Pennisula of Michigan has good views that are accessible from a wheelchair. There is a boardwalk that offers several good views of the lower waterfalls with a viewing area a third of a mile from the parking lot.
The upper falls has a drop of more than 50 feet and is 200 feet across. A paved pathway leads from the parking lot to the observation platforms. There are steps down to the lower level, but the view from the top is pretty good. 
If you only have time for one of them, the lower one was a nicer walk with several places to look over the falls. The amber color of the water is caused by tannin from the Cedar, Spruce and Hemlock in the swamps drained by the river. The soft water churned by the falls action causes foam as well.