The first waterfall that you encounter on the Cascade River is logically called Cascade Falls. Further beyond that are The Cascades. This first falls is a rather short distance from the trailhead, and it is definitely worth it to go and visit both “sets” of falls.
Unlike the Cascades, which is a complex set of…cascades, Cascade Falls is an actual plunge waterfall. I visited the falls in mid-May 2010, and the falls were at their prime then, most likely due to recent snow melt. (It had actually snowed just three days before, though that disappeared pretty quickly, and the temperatures returned to a state of relative comfort.) I imagine these falls are probably less impressive in the depths of the summer, but the hike is still enjoyable. The best view of the falls is found on the left side of the river (as you start).
1) The parking area for The Cascades and Cascade River State Park are found off of MN-61 a few miles south of Grand Marais. The parking area is on the left side of the road if you are driving north.
2) After finding the parking area for the falls, you can head upstream on either side of the river, but I started on the south side. That seems to provide better views of the falls.
Where in the World is Cascade Falls?: map