It's free the whole month of September. What i did is I got there early with my family used street parking stayed there for two hours and parking was 4 dollars. If you can manage to have someone in your group leave the sheds after an hour and a half to feed the meter again every two hour you can stay longer and pay half the parking fee
If you can get street parking that is metered it's around 2.00 an hour ,but that fills up fast. If you get there before 9am , both street parking and the lot down by Adler's are good options. The lot by Adler's has an early bird special for under 20.00 for the day if you get there by 9am. If there is something going on at Soldier Field, parking fills fast and will cost more.
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