We are looking east along West 123rd Street in this view from Amsterdam Avenue. This is the northern boundary of the park. We see the Block House No. 4, a remnant fortification built but never used to defend the city in the war of 1812. PS 36 now sits on this same outcropping. One of the other block houses built at this time still survives in the north woods of Central Park.

Block House #4, ca. 1905. Block House #4 sat on the massive glacial rock outcropping at 123rd Street and Amsterdam Avenue. It was one of a series of stone defense fortifications constructed around the War of 1812. Despite the preparation for the perceived threat of British invasion, the British never made it to Manhattan during the war. The ruins of Block House #4 remained on the outcropping until the 1960s when Public School 36 was constructed on the site. The sections of the school where built directly on the large rock, which can still be seen on the 123rd Street side. A single block house survives in the northern section of Central Park; it is also situated on a large rock outcropping.

While New York City is certainly best known for its towering skyscrapers and classy historic districts, its earliest monuments of stone are just that: stone. The geologic landscape of the city was formed between 20,000 and 18,000 years ago with the movement of the Wisconsin Ice Sheet down from Canada. The rock and debris deposited from the ice sheet, as well as the valleys it deepened, bedrock it smoothed and glacial grooves it left, formed the landscape of the city that began to grow in the colonial era. In some cases the rocks have been moved or crumbled in the name of urban development. But some of this geologic history can still be seen within the urban environment. This collection highlights some of the more well-known geologic features.

Another view of the Block House No. 4 and the exposed manhattan schist face where West 123rd Street was cut through at the northern termination of the park. As we’ve seen in this story, the geology and resulting dramatic topography of a ridge of Manhattan Schist is a defining feature of Morningside Park. In fact, it’s only due to the daunting nature of this rock that Andrew Haswell Green decided to not extend the east-west street grid through this part of Manhattan and instead called for a park to be designed and constructed on this land.

This is part of Urban Archive's "Arms and Armories: Fort Week," a series that features a week of stories about the military installations that once defended the city. When we look at the remains of forts and armories around the city today, it might now seem strange to imagine ships arriving in New York Harbor and seizing the city. Well, that's exactly what the British did in August of 1664 and July of 1776. This set of military installations were built during the last three hundred years to gird New York with defenses that ensured the protection of America's financial hub.