This image shows the body of water known as Lake Pepin. It is in fact a natural lake formed by a widening of the Mississippi River at this point, so it is also part of the river course. In the far background is a large bluff overlooking the lake called Maiden Rock.
There is no description on the back of the card.
The legend is that a Dakota Princess jumped to her death after her lover, a man from the rival Chippewa, was killed on the orders of her father, a chief of the Dakota.
This card likely dates from the 1940s.