New York is a city that’s fairly hostile to people who just have to go. The city used to be studded with public bathrooms here and there; most early BMT and IRT stations contained public restrooms, and that’s why you often see MEN and WOMEN tiled or terra cotta signs by locked doors. The vast majority of subway bathrooms have been turned into storage rooms.
The reasons for this are simple. There are predators among us and there always will be. There are also vandals among us who deface property because it is there to be defaced. These bathrooms needed to be cleaned and frequently disinfected, and all that costs money. The city does have some public bathrooms remaining — the one in Bryant Park is said to be among the city’s best. By and large, though, it’s best to hold it in until you can find a playground: I always try to have my ForgottenTour routes go past a public park with a public bathroom, since they’re reliably open during the warm months. They’re not the cleanest, but the deed can be done safely and without a whole lot of embarrassment.
There’s a former public bathroom on the center median of Allen Street at Delancey. It was most likely built as a Works Progress Administration project. Most of its detail, including carved MEN and WOMEN signs above the entrances with light sconces are still there. In addition, the New York State seal in bas relief is affixed between them.
You can see the Allen Street bathroom on the right of this 1940 photo from the Municipal Archives. At the time, the 2nd Avenue El ran down the west side of Allen Street, and it was carried over the extra-wide Delancey Street on an iron trestle (the West Side Highway had the same solution at Canal Street and in Brooklyn, the Myrtle Avenue el got across the Flatbush Avenue Extension on a similar iron bridge).
In 2016, permits were acquired to turn the former bathroom into a food vending venue, but nothing seems to have happened yet with that effort.