The Concourse Line is an IND rapid transit line of the New York City Subway system. It runs from 205th Street in Norwood, Bronx, primarily under the Grand Concourse, to 145th Street in Harlem, Manhattan. It is the only B Division line, and also the only fully underground line, in the Bronx. Description and service The following services use part or all of the IND Concourse Line: The Concourse Line runs north to south through the Bronx and portions of Harlem, parallel to the mostly-elevated IRT Jerome Avenue Line which lies between two and four blocks to the west for its entire length in the Bronx. Due to the steep topography of the neighborhoods surrounding the Grand Concourse (under which most of the line runs), several stations were built with entrances both above and below the platforms, including 167th Street and Kingsbridge Road. Because the line also connected with Yankee Stadium at 161st Street and with the former Polo Grounds at 155th Street, there were also several switches and a storage track to accommodate additional trains during game days. The line begins as a two-track line at Norwood–205th Street, running east-to-west underneath East 205th Street, then under private property, then for a short portion under Van Cortlandt Avenue. As it travels west, a center track forms which leads to the Concourse Yard. The line then curves south at Mosholu Parkway to the Grand Concourse, from which it derives its name, at 206th Street. Two tracks from the Concourse Yard arrive between the two revenue tracks with switches and diamond crossovers between all four of them before the yard tracks merge to form the center track at Bedford Park Boulevard. The center track was intended to be used by southbound express trains in the morning and by northbound express trains in the afternoon. South of this station, the two outer tracks depress into a lower level and merge into a single center express track, while the center track splits to become the local tracks. The line then runs south with diamond crossovers at Tremont Avenue. Due to the terrain, the vicinity of 174th–175th Street station is uniquely built both underground and over 175th Street. Between 170th Street and 167th Street are more switches and crossovers, with a lay-up track adjacent to the Manhattan-bound local track. The line curves west before 161st Street–Yankee Stadium and crosses the Harlem River into Manhattan via