Named after 23rd Street, the southern edge of a planned military parade ground.
The Commissioners’ Plan of 1811 reserved the land between 23rd and 33rd Streets and Third and Seventh Avenues as the ‘Grand Parade’, an open space for military training and an assembly point in case the city was invaded. The ground was gradually reduced: by 1847 only 7 acres remained, the land of today’s Madison Square Park.