A first-class letter mailed through the U.S. Postal Service takes, on average, three days to go from Tennessee to Chicago, according to the USPS map server. The Postal Service does not guarantee three-day delivery although first-class delivery generally takes two to three days.
It costs 49 cents to mail a first-class letter weighing up to 1 ounce, as of July 2014. Delivery time from central Tennessee to extreme southern Illinois is normally two days; however, first-class mail normally takes three days to reach Illinois from Tennessee. Letters can be delivered faster using the Priority Mail or Express Mail options, which have higher costs.