Druid Hill Park was inaugurated in 1860 and is listed on the National Register of Historic Places, totaling 745-acres (300-hectare) in size. Druid Lake was constructed (1863-1871) to provide a one-billion-gallon capacity, 55-acre (22-hectare) freshwater reservoir supplying the City of Baltimore and surrounding counties with drinking water. The lined temporary stone cofferdam was a critical component of a much larger, $164 million, five-year project to modify the existing Druid Hill Reservoir.