Why is Minnehaha Falls so much narrower than it used to be?

Listen and subscribe to our Curious Minnesota podcast: Apple Podcasts | Spotify

The older the postcard, the wider the falls.

That’s what a reader who collects vintage Twin Cities postcards noticed as he looked through some featuring Minneapolis’ long-beloved attraction, Minnehaha Falls.

The difference was striking: In images from more than a century ago, the waterfall appears to be much, much wider than it is today.

He wrote to Curious Minnesota, the Strib’s audience-powered reporting project, to ask: “What led to the narrowing of the falls?”

The difference is not an illusion. Minnehaha Falls are “absolutely” narrower today, said historian Dave Smith, the author of “City of Parks: The Story of Minneapolis Parks.”

“I have a lot of stereographs from the 1800s, and there were times when it looks like the flow of water must have been 30, 40 feet wide,” Smith said.

At the same time, as the creek’s water has continued to erode the lip of the falls, it has cut a narrowing notch into the limestone. This keeps the falls flowing in a relatively slim ribbon even during rainy weather.

Though the years, park leaders have fretted about the flow of water over Minnehaha Falls and the ways that that erosion would change the waterfall’s appearance.

“The erosion of the lip of the falls has been a concern for more than 100 years,” said Smith.

In 1906, Charles Loring, who served as the Minneapolis Park Board’s first president, proposed using concrete to shore up the falls. “Time to act if Minnehaha Falls are to be saved,” the Minneapolis Journal blared across its front page that September.

“The danger of a possible collapse of the limestone ledge of Minnehaha Falls has been recognized for some time. … There is no question but that the Falls have receded from the Mississippi during the centuries,” Loring told the newspaper. “I believe it would be a wise precaution to give the limestone ledge some sort of artificial and more permanent support than it now has, and that such a support could be placed there without in any way marring the beauty or the artistic perfection of the choicest show place in the park system.”

The creek’s waters continue to carve into the ledge, and the falls have receded through the years. The changes have not been as dramatic as leaders 120 years ago once worried they would be, but the falls’ geology does mean that at some, point erosion will speed up, Smith said.

“The top layer there is limestone, and below that is sandstone,” he said. “And so once that limestone goes, the lip of the falls is going to retreat pretty far, because the sandstone below the limestone will erode much, much faster.”

In winter, icicles often do span the wider lip, giving a glimpse of the grand curtain that once flowed there. The icicles are created by groundwater flowing through the limestone layer.

As January’s extreme cold snap began, the entire gorge was draped in ice.

If you’d like to submit a Curious Minnesota question, fill out the form below:

Are those really LBJ’s footprints in concrete at Minnehaha Falls?

How a 40-ton grain elevator crossed over the Rapidan Dam

Why did Minneapolis bury Bassett Creek?