the connection between the two lines approved on March 24, 1927. The line was originally intended to be four tracks, rather than three tracks, to Bedford Park Boulevard. This is the only IND line with three tracks (all other IND lines have either two or four tracks). The Concourse line's lower level of the 145th Street station was originally provisioned for four tracks, with the current tracks lining up with those of the upper level.

Construction of the line began in July