Henry is a city in Marshall County, Illinois, United States. The population was 2,464 at the 2010 census. It is part of the Peoria, Illinois Metropolitan Statistical Area. Henry is named after General James D. Henry, and was initially surveyed in 1834. 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. Its slogan, “Best Town in Illinois by a Dam Site,” is derived from the city’s distinction of having the first lock and dam built on the Illinois River. It was completed in 1870 at a cost of $400,000.The retreat house of the Roman Catholic Diocese of Peoria, Illinois (Nazareth Retreat House, formerly, King’s House) is located here.
Henry is located at 41°6′47″N 89°21′37″W (41.113152, -89.360218).According to the 2010 census, Henry has a total area of 1.392 square miles (3.61 km2), of which 1.32 square miles (3.42 km2) (or 94.83%) is land and 0.072 square miles (0.19 km2) (or 5.17%) is water.Henry lies on a segment of a river terrace that is about 14.5 kilometers (9.0 mi) long just over 6.5 kilometers (4.0 mi) wide. This fluvial terrace is underlain by stratified; yellowish brown to grayish brown; calcareous; and usually clean and moderately well sorted sand and gravel with cobbles and boulders. These sands and gravels contain occasional beds of silt and clay and unconformably overlies older sand and gravel deposits, glacial till, or bedrock.
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