Mapleton is a small village in Peoria County, Illinois, United States. The population was 227 at the 2000 census. Mapleton is part of the Peoria, Illinois Metropolitan Statistical Area. There are four different plants in Mapleton, all located along U.S. Route 24: an Evonik chemical plant, a Lonza Group plant, a Caterpillar Inc. foundry, and an Ingredion facilit…Mapleton is a small village in Peoria County, Illinois, United States. The population was 227 at the 2000 census. Mapleton is part of the Peoria, Illinois Metropolitan Statistical Area. There are four different plants in Mapleton, all located along U.S. Route 24: an Evonik chemical plant, a Lonza Group plant, a Caterpillar Inc. foundry, and an Ingredion facility; together, the large industrial complex forms one of Mapleton's most significant employers and a good source of skilled employees and good jobs.