Chestnut is a census-designated place in Aetna Township, Logan County, Illinois. As of the 2010 census, its population was 246. The community is located northwest across the railroad tracks along Illinois Route 54 at Dauphin Street. Its claim to fame, for the sake of town promotion, is that it is the geographic center of the state. A small monument to this effect has been erected in a park near the southwest corner of Melvin Street and East Olive street (in §34 T19N R1W). However, the exact center of Illinois is about eight miles southwest of Chestnut, and on the other side of the town of Mount Pulaski, at 89°18.4'W 40°0.8'N.
The population was spread out with 72.0% over the age of 18 and 15.4% who were 65 years of age or older. The median age was 37.5 years. The gender ratio was 47.6% male & 52.4% female. Among 99 occupied households, 88 were owner-occupied & 11 were renter-occupied.