Sentry Security Agency has been protecting the St. Louis Metropolitan Area for over 45 years. We provide on-site security officers for both commercial and residential customers. We are a family-owned local business. The Mueller Family, who own and operate Sentry Security, are proud of their heritage which includes three generations of U.S. Marines and three generations of the St. Louis Metropolitan Police Department. Our Directors and Managers have over 20 years experience working directly in the security industry.