Railroad apartment

[3][4][5][6][7] This style is most common in New York City, San Francisco, and their surrounding areas.

Railroad apartments first appeared in New York City in the mid-19th century, and were designed to provide a solution to urban overcrowding.

[8] Many early railroad apartments were extremely narrow, and most buildings were five or six stories high.

[8] Few early buildings had internal sanitation, and bathrooms emptied raw sewage into the back yard.

[8] In some cases, one family would take up residence in each room, with the exterior hallway providing communal space.