The Susquehanna Power Company built a police sub-station at Conowingo for the use of the Maryland State Police in 1929, leasing the land to the agency for $1 a year. When it opened that April, a staff of two sergeants, a corporal and four officers were assigned to the post. It was modern with offices, a kitchen, a cell room, and sleeping quarters for twelve men. In addition to motorcycles for the patrol, one horse was detailed to the post.
The force consisted of First Sergeant Atkinson, Sergeant Katz, Corporal Dyas, and Officers Weber, Klapproth, Phillips and Holland. The troopers were centrally located to handle the increasing traffic on Route 1 and they policed Harford County north of Deer Creek, Cecil County, and Kent County.
In an era when ambulances weren’t commonly available, the Maryland Police responded to the need for medical transport and quick response to automobile accidents. The agency acquired five ambulances in 1935, and one of those units was assigned to sub-station F at Conowingo.
Over the years, additional barracks were constructed to meet the growing demands for police service and operations at Conowingo were scaled back. At some point in the early 1970s or late 1960s, it was scaled down from a 24-hour-a-day to an 8-hour operation. On September 1, 1973, the old station passed into history as it was deactivated. It was the oldest installation at that point, having served the public for 43 years, but barracks in North East and Bel Air provided greater coverage to northeastern Maryland.