[3] In 1850, the cut was roofed over[4] using granite stringers from the original railroad bed south of 14th Street, creating the present tunnel.

[7] Several prominent businessmen and property owners including J. P. Morgan Jr. and Charles D. Wetmore opposed the plan.

[8] Some residents alleged the plan would damage nearby properties, while others objected that a flattened 34th Street would allow the construction of a moving walkway, "ruining" the residential character of the neighborhood.

At that time the north end was reconstructed with a steeper approach, reaching street level south of 40th St and allowing continuous car travel from the tunnel onto the viaduct.

[5] Prior to August 3, 2008, the tunnel carried two-way traffic, one lane for each direction; on that date, it was made northbound-only to increase safety for pedestrians crossing Park Avenue at 33rd Street.

[13] In 2013, the tunnel was open to pedestrians for the first time in coordination with the annual Summer Streets event, which shuts down part of Park Avenue to vehicular traffic between 7:00 am and 1:00 pm for three Sundays every August.

[14] In the 2014 Summer Streets, the tunnel temporarily reopened to pedestrians, this time featuring DIVE, an installation by Jana Winderen that incorporates aquatic soundscapes.