I live in Rockford and didn't even know about it. Ive been hunting Lowden Miller in Oregon for 7 or 8 years. It gets some pressure, but you can do some walking down the main trails to get away from the parking lots. There are a lot of clear-cuts that are really overgrown. The deer get in there and are fairly secure. You cant get anywhere near them without making some serious noise. I have seen some nice deer, but usually early season, or on the tail of a doe during the rut. Pretty sure the big boys go nocturnal the second they feel pressure. I have become very familiar with several parts of the park, and enjoy hunting there.
There is also Castle Rock on the other side of the Rock River.
I can get to Lowden Miller in 45 min from my house in Rockford.