This subway power substation at 144th Place and Jamaica Avenue was built around 1966-67 to "[provide] additional capacity to meet higher power demands of the new high acceleration type cars on the Broadway-Jamaica Line". The easternmost portion of that elevated line, which once stood adjacent to the substation on Jamaica Avenue, was closed in 1977 and has since been demolished, along with the rest of the line east of about 127th Street. The Wikipedia page on the Broadway-Jamaica Line (a.k.a. the Jamaica Line) claims that the substation is now used for the nearby underground Archer Avenue extension of the Jamaica and Queens Boulevard Lines that opened in 1988.