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.

Rock outcrop on Magenta Street, east of White Plains Road, June 16, 1938. The land to the left would be set aside for the New York City Housing Authority’s Gun Hill Houses, a six-building development which opened in 1950. The rock formation is still visible on Magenta Street.