Grant Park is a place I have been going from my whole life. My parents took me there as a kid and it used to be part of my running trail, so I have been observing it now for more than a half century. There have been many changes in the forest cover.
The natural forest is beech-maple-basswood. But they planted lots of exotic trees, so you get examples of scotch pine, Norway spruce, Norway maples, white birch and larch. Parks of the woods are really European with the species mentioned above dominating.
In the time I have known Grant Park, the birches have largely disappeared. They do not naturally reproduce in the Milwaukee area. These were not North American birches, in any case. They planted European white birch. The Scotch pine will be gone soon. They do not live that long and also will not naturally regenerate. The Norway spruce will not regenerate either, but they live a long time and will be here long after I am not. Norway maple do and are regenerating. They look much like sugar maples. You can tell the difference by their bark and more easily by their seeds. They seem to occupy the same niche as sugar maples but can be rather more successful, since they better tolerate city conditions. They are pretty, but could be considered invasive.
My first picture is one of the European forests. Nothing in the larger trees is natural. There are white pine, native to Wisconsin, but not to Milwaukee County. Most of the rest are from farther away, Norway spruce, Norway maples, Scotch pine and European white birch. The next picture shows the white birch. They will soon be no more. Picture #3 is natural forest with native species and finally is the Lake.