It’s that fence that helps date this picture. Most likely it was taken after the scandalous 1857 purchase of Fort Snelling by Franklin Steele and his shadowy partners from Back East. That was the first time that Steele owned the Falls of Minnehaha.
One of the little details that is so great about this picture is the entrance to the ice cave on the far left. That opening is recreated by the freezing icicles every year.