Seneca is a village in LaSalle and Grundy counties in the U.S. state of Illinois. The population was 2,353 at the 2020 census, down from 2,371 at the 2010 census. The LaSalle County portion of Seneca is part of the Ottawa Micropolitan Statistical Area, while the small portion that lies in Grundy County is part of the Chicago–Naperville–Joliet Metropolitan Statistical Area. History The village of Seneca, formerly named Crotty after our founder, Jeremiah Crotty, was incorporated in 1865. Our town was created during the construction of the Illinois & Michigan Canal for which Crotty was a contractor. The Rock Island Railroad and the Illinois River also supported the creation and business of our town. Seneca is most known for its contributions during World War II when Chicago Bridge and Iron operated the Prairie Shipyard. 157 Landing Ship Tanks (LST) were built here. Geography Seneca is located at (41.3111442, -88.6097936). According to the 2021 census gazetteer files, Seneca has a total area of , of which (or 94.42%) is land and (or 5.58%) is water. Most of the village lies in LaSalle County, although a small portion extends into west central Grundy County. In the 2000 census, all of Seneca's 2,082 residents lived in LaSalle County. According to 2006 population estimates, 2,082 of the village's 2,087 residents (99.8%) lived in LaSalle County and 5 (0.2%) lived in Grundy County. Seneca is located on the Illinois River, which connects Lake Michigan to the Mississippi River. Demographics As of the 2020 census there were 2,353 people, 950 households, and 758 families residing in the village. The population density was . There were 939 housing units at an average density of . The racial makeup of the village was 90.95% White, 0.85% African American, 0.55% Native American, 0.47% Asian, 0.08% Pacific Islander, 1.15% from other races, and 5.95% from two or more races. Hispanic or Latino of any race were 4.38% of the population. There were 950 households, out of which 69.05% had children under the age of 18 living with them, 48.95% were married couples living together, 19.89% had a female householder with no husband present, and 20.21% were non-families. 11.68% of all households were made up of individuals, and 6.11% had someone living alone who was 65 years of age or older. The average household size was 2.85 and the average family size was 2.67. The village's age distribution consisted of 26.3%