"For instance, there is a brownstone in the East Seventies"

Brownstone, Upper East Side NYC
Creative Commons AttributionBrownstone, Upper East Side NYC - Credit: 1hr photo

Brownstone is a type of brown sandstone that was once a popular building material. In the US, the term is used to describe terraced housing built from this material. 

Brownstones are common in a number of New York City neighborhoods, particularly in Brooklyn and Manhattan’s Upper West Side.