All About the Shotgun House

A shotgun house is so named because you can stand at the front door, fire a shotgun and see your slug fly straight through the house and out the back door. Shotgun houses are generally under 12 feet wide and have three to five rooms in a row, starting with a living room, with bedrooms in the middle and ending with a kitchen at the back.
Shotgun houses are usually built about three feet off the ground and have wood frames and small front porches. Sometimes there aren't even windows on the sides of shotgun houses because they were built so close to neighboring homes that sunlight wouldn't be able to reach side windows.

Shotgun houses developed after the Civil War in New Orleans and remained popular through the 1920s across the South, according to Wikipedia. The style gradually became associated with the poor.

There are variations on the shotgun house. "Double-barrel" shotgun houses have two straight homes side by side, sharing a center wall. "Camelback" shotgun houses have a raised second story on the back.

The floorplan of a shotgun house had two main benefits: it allowed developers to fit more homes on a single block, and it allowed for increased airflow in the days before air conditioning.

See This Old House's renovation of a New Orleans shotgun house.