Henry is a city in Marshall County, Illinois, United States.

[3] The topography of the land on the west side of the Illinois River, with relatively steep banks rising well above river level, assured early settlers that their homes would not flood.

[5] It is bordered to the east by the Illinois River, which forms the boundary with Putnam County.

Illinois Route 18 passes through the center of Henry as Third Street and School Street, leading southwest across the Illinois River on the Henry Bridge, then east 28 miles (45 km) to Streator.

Illinois Route 29 passes through the west side of the city, leading north and east 24 miles (39 km) to Spring Valley and southwest 33 miles (53 km) to Peoria.

[6] The sands and gravels underlying the terrace on which Henry lies were deposited by the Kankakee Torrent about 19,000 BP calibrated years ago.

[7][8] Within the Illinois River valley, these sediments typically range from 10 to 80 feet (3 to 24 m) thick.

29.8% of all households were made up of individuals, and 16.9% had someone living alone who was 65 years of age or older.