Douglass Houghton Falls
The tallest waterfall in the Keweenaw by far, Douglass Houghton Falls measures 120 feet from top to bottom. It's easily the most impressive waterfall in the area, particularly during the spring melt (pictured above). It also happens to be one of the most hard-to-get-to falls and as a result is somewhat unknown relative to other nearby waterfalls. On the way there you'll find the remains of an old train bridge that crossed Hammell Creek. A bonus feature of this waterfall is the exploratory mine adit that runs underneath it from the south bank of the creek. It goes into the cliff about 300 feet or so. You will need a flashlight to get to the end of it.
Some things to note: wet rocks are very slippery, particularly at base of the falls. Wear good shoes. The rock surrounding the adit seems competent so there shouldn't be any safety issues there. The ceiling is low though so watch your head. Lastly, the north slope of the gorge has a garden of poison ivy growing on it. If you're allergic or don't want to find out, keep off of it! The active oils still remain on the woody stems even after the leaves have fallen off.
To get here from Houghton, head north on the lift bridge and turn left onto M-26. Drive for 11 miles until you get to 10th street. Turn right here and drive two blocks. Turn left onto Gregory Street and drive about 2500 feet until you get to the Hammell Creek culvert bridge. There's a small parking area immediately to the right. Cross the road and head west. There is a small trail that loosely follows the creek upstream to the snowmobile trail grade. When you get to that, Hike up and back down the other side and continue up the trail until you get to the falls. The hike should last about 20-30 minutes one way depending on your fitness level. If you loose the trail, don't panic. Continue to follow the creek upstream and you will get to the falls no problem.
An alternate route would be to continue straight on M-26 to Calumet Street, turn left on 13th street, park at the snowmobile trail, and hike to Hammell Creek. This might shave 5 minutes off of the hike but you'll need a 4 wheel drive vehicle with adequate clearance to get to this point.