Named after First Avenue, where the numbering of Manhattan's 1811 avenues begins.
The Commissioners' Plan of 1811 laid out twelve broad avenues running the length of Manhattan, numbered from First Avenue on the east side to Twelfth Avenue in the west, with lettered avenues A to D further east. Further north, First Avenue's stretch between 42nd and 48th Streets was renamed United Nations Plaza in 1952, and its many hospitals earned it the nickname 'Bedpan Alley'.