It’s rare that Minnehaha Falls truly freezes completely. Even in the coldest winters, when you climb up behind the waterfall you can hear the trickling of moving water. Sometimes you can see the water moving through the ice.
The lip of the waterfall is more narrow than it used to be, and indeed has been getting narrower in the last 10 years with erosion. But every winter we see a wide curtain of icicles all across the western side of the Minnehaha Gorge. They are created by groundwater moving through the limestone layer that creates the lip of the falls. Starting in 1889, the Park Board has done a lot of work to de-water springs and redirect that groundwater, and much of that work has been successful. But the icicles still form.
On January 9, 2017, the Star Tribune newspaper reported that a woman had been hurt behind the falls. She was struck by a falling icicle and was not seriously hurt, but was taken to the hospital. This is the most recent story of someone being hurt by an icicle coming lose behind Minnehaha Falls. The first report was an incident from November 26, 1869.
The winter of 2016-2017 has come after an unseasonably wet year, and the temperatures have not been severely cold. In the second week of January, 2017, the falls are still flowing freely. The early winter of 1869-1870 was also after a very wet growing season, and had surprisingly warm temperatures. Torrential rains were reported in September of 1869. The Mississippi River was so high that the Fort Snelling rope ferry was declared unsafe. Temperatures in late November 1869 were often about 30F, after some colder days in October.
And this combination of plenty of ground water and near-freezing temperatures makes the icicles behind the Falls a terrible danger. On that Friday afternoon in 1869, the well-known photographer Charles A. Zimmerman had come over from St. Paul to see (and probably photograph) Minnehaha Falls. He made his way back behind the waterfall. And then quite suddenly, an icicle reported to weigh between 200 and 300 lbs. came loose from the overhang and fell on him. He was knocked unconscious and laid there alone for more than 30 minutes.
Happily for him, a visitor from Chicago named Haines also went exploring behind the waterfall that day and discovered Zimmerman. He got some help, got Zimmerman conscious, and helped him back up the southside bluff to Captain Palmer’s roadhouse next to the Falls where Zimmerman “was soon revived by the application of proper restoratives.” (This refers to liberal shots of whiskey and a chair by the fire.) Zimmerman was badly bruised but managed to hobble home on the evening train. There were no broken bones.
The historical weather information here was recorded at Fort Snelling, and is presented on-line at climatestations.com.