BikerBoy from Maryville, IL on 9/2/2019 2:28:55 PM:
Larry, happy to help. I just finished riding about 350 miles of trails in your beautiful state last week (actually drove through Birch Run).
You may leave your car in the parking lot at Frontier Park in St. Charles, right near the river and on the Katy Trail. Best place is near the boathouse under one of the parking lot lights. I strongly suggest that you notify the St. Charles Police that it will be there for the amount of time you specify so that it does not get towed.
Some people have suggested leaving a note in the dashboard with your cell number in case they need to contact you. I dunno. Definitely remove all your valuables from the car or at least make them invisible. It's not a bad area at all, but the number of days parking means the chance increases.
Have fun!