The main line ceased operation in June 1940,[2][3] after it was replaced by the IND Eighth Avenue Line which had opened in 1932. The last section in use, over the Harlem River, was known as the Polo Grounds Shuttle. It closed in August 1958.[4] This portion used a now-removed swing bridge called the Putnam Bridge,[5][6] and went through a still-extant tunnel with two partially underground stations.[7]
^Shaw, Robert B. (1961). Down Brakes: A History of Railroad Accidents, Safety Precautions and Operating Practices in the United States of America. London: P. R. Macmillan. OCLC2641112.
^Reed, Robert C. (1978). The New York Elevated. South Brunswick, NJ and New York: Barnes. p. 138. ISBN0-498-02138-6.