The island has not always been forested; early French explorers found it flat and grassy. At its tip, we found this floral marker, obviously fresh:
The island is sacred to the Dakota Indians, whose possession of the Minnesota land came to an awful end at Fort Snelling, on the western shore above, in 1862, where they were interned (many dying of starvation) and then expelled from the state. The battle started 150 years ago in Friday, and the anniversary is being marked by a series of articles about the Dakota chief Little Crow in the Star Tribune. 
I found a picture of what things looked like before the the crisis later in the day, while making my way through the wonderful Minneapolis Institute of Arts, Edward K. Thomas' c. 1850 View of Fort Snelling.