It’s Gas Price Monday. AAA says the average price of a gallon of regular gas in Illinois is $2.27. That’s up seven cents from last week’s average of $2.20 per gallon, but down seventy-four cents from the average price a year ago, which stood at $3.01 a gallon. Danville, Illinois had the lowest price in the state this week, at $2.08 a gallon. The highest price was in Chicago, at $2.63 per gallon. The average price in Rockford was around $2.14 a gallon.