The West Side school perched on top of a massive rock pile
Not many cities have a type of rock named after them, but Manhattan has Manhattan schist—an ancient bedrock formed roughly 450 million years ago.
Manhattan schist generally lies underground, providing the ideal strong foundation for the skyscrapers clustered in Lower Manhattan and Midtown, where the schist is closer to ground level and better able to anchor massive buildings.
But some schist lies above ground in the form of giant amazing rock outcroppings. Case in point: this high pile of gray, grainy schist on West 123rd Street east of Amsterdam Avenue in Morningside Heights.
Even in New York City, which from its very beginnings flattened and filled in the natural topography to fulfill real estate needs and dreams, schist like this was tough to deal with. For most of the 19th century, the pile was the site of blockhouse number 4–one of several small stone forts built to hold munitions if needed to defend Gotham during the War of 1812, per Harlem + Bespoke.
By the end of the 19th century, the schist and the unused blockhouse were part of Morningside Park. This steep, schist-filled green space became a park in part because Parks commissioner Andrew Haswell Green thought it would be “very expensive” and “very inconvenient” to extend the Manhattan street grid to such a rocky area, according to NYC Parks.
123rd Street looking east from Amsterdam: the remains of the 1812 Blockhouse are on top of the rocks In the 1960s, however, the city was casting about for a site to build a new elementary school in or around Harlem. “The state legislature and mayor supported the construction of a school on the north part of Morningside Park, where the ruins of Blockhouse 4 were,” states the website for the Margaret Douglas School, also known as PS 36.
Construction of the school began in 1965, the ruins of the blockhouse were bulldozed away, and a new elementary school rose on this prehistoric heap of Manhattan schist.
The school is still in use, a Brutalist-style building stacked on top of the massive rocks with the help of concrete risers. It’s not far from another Manhattan schist outcropping: the enormous rat rock on West 114th Street, which was apparently too expensive to dynamite away and remains wedged between two apartment buildings.
[Third image: MCNY, F2011.22.1574]
