HH was the last of the letters assigned to original routes of the Independent Subway System of the New York City Subway in the 1930s. It was designated as the dedicated service letter of the IND Fulton Street Line in Brooklyn. The letter was intended to be used for a service running local from Court Street, a stub-end station in Downtown Brooklyn, to the future Euclid Avenue station near the border with Queens. Express service on the four-track line was to be provided by trains coming from Jay Street–Borough Hall and Manhattan.