Grand Army Plaza opened on October 10, 1920 as part of the opening of the IRT Eastern Parkway Line, an extension of the Brooklyn IRT from Atlantic Avenue to Eastern Parkway - Brooklyn Museum [REF].
During the 1964-1965 fiscal year, the platforms at Grand Army Plaza, along with those at four other stations on the Eastern Parkway Line, were lengthened to 525 feet to accommodate a ten-car train of 51-foot IRT cars [REF].