O'Fallon Police Department

Education, prevention and enforcement are the three tools the O'Fallon Police Department names in its mission of solving problems proactively and protecting life and property. The Illinois city it serves, home to many personnel from nearby Scott Air Force Base, counted an estimated 32,656 residents in 2025 in the Census Bureau's Vintage 2025 data. Patrol is the department's largest component, with thirty-seven full-time officers working four 12-hour shifts, each built around a sergeant and seven officers, under two watch-commander lieutenants and a captain. The city is divided into three zones, each with an assigned officer, plus two roving officers. Follow-up work on reported crimes falls to the Criminal Investigations Division, whose detectives interview victims and witnesses, process scenes and prepare cases for the St. Clair County State's Attorney or a federal magistrate. In partnership with O'Fallon Township High School District 203, an officer is assigned there full-time during the school year. A Community Service Officer program lets adults interested in policing work side by side with full-time officers while supporting each division, and the department has been accredited through the Illinois Association of Chiefs of Police's Illinois Law Enforcement Accreditation Program since 2018, most recently recognized in December 2024.

According to the U.S. Census Bureau (ACS 2023), O'Fallon city, IL has an estimated population of 32,139.