The New York City Department of Plant and Structures was an operator of transit in New York City. In September 1919, Mayor John Francis Hylan charged the department with organizing private entrepreneurs to operate "emergency" buses to replace four abandoned storage battery streetcar lines: the Madison Street Line, Spring and Delancey Streets Line, Avenue C Line, and Sixth Avenue Ferry Line. The system gradually grew, taking over various lines including the Brooklyn and North River Line (trolleys) and Queens Bus Lines (buses), and the DP&S also began operating trolleys in Staten Island to replace the Staten Island Midland Railway's system. Eventually all of these routes were transferred to private management.