The Lexington Ave line from north of Grand Central to South of 110th St is constructed on two levels, probably to avoid opening Lexington Ave four tracks wide during construction. The only station on the express tracks was at 86th Street. Over the years from the July 17, 1918 opening the east side built up to the point that the local trains couldn't handle the crowding. Since the 59th Street station was a transfer to the BMT, this was the logical place for a express stop.
Here is a series of scans of the flyer given out on opening day of express service on November 15, 1962. Click on each image for large display.
- The JoeKorNer