I finally had a chance to visit the US First Infantry Division museum, at Cantigny park, located in Wheaton, IL. While I had known about the tank park and the gardens, I didnt know until recently that they had archival information related to the 1st infantry division.
The library is located in the bottom floor of the 1st infantry division museum, and is staffed by some very helpful people (thanks Mary !). For WW2, they have all the archival records available at NARA, and some photo archives. I am unsure if the photos at Cantigny are available at NARA.
As it relates to German units, the records at Cantigny include the G-2 files which I have found to be very useful in locating and identifying German units for the time period of Sept-Dec 1944.
They have a typical microfilm reader and printer, but they also have a ScanPro2000 which I found to be very handy. You can view and save files in digital format and I hope that NARA gets one of these units.
While they are closed in January, they otherwise have typical operating hours of 10-4 PM on the weekdays. If you are in the area and you are interested in the 1st infantry division (not just WW2, but several conflicts), then I highly recommend visiting there.