The passage describes the development of row houses as a form of urban housing in the United States during the late 19th century. [1] Speculative builders found row houses highly profitable to construct because they shared walls and could be built side by side on narrow lots. [2] Row houses proliferated in many American cities, with wooden versions appearing light and airy in style on the West Coast while those in New York were most often faced with brownstone. [3] San Francisco developed a particularly successful model of the row house that was suitable for people across economic classes.