During World War One, American involvement in the war brought the historic DEP Police to duties protecting the NYC water supply. As of the current today 2019, the DEP Police today still has the same mission guarding the water supply, and is a participant of the annual First Provisional Regiment memorial services, held at the Village of Sleepy Hollow, NY. This Aqueduct Defense Memorial Service honors and remembers 40 soldiers who died while serving New York State during World War I. DEP Police provides an honor guard, cooperates with the NY state defense force, and local government officials to remember those perished while on aqueduct duties.
During World War One, American involvement shifted the historic DEP Police's focus from general law enforcement to protecting NYC's water supply. The DEP Police remains committed to safeguarding the water supply and pays tribute to those who lost their lives while serving in this capacity through annual memorial services.