A Flounder House
"The flounder is a narrow house, usually two or two and a half stories tall, and one or two bays wide. These houses were exclusively working class homes. Flounder houses were especially appropriate for dense neighborhoods, where space was at a premium. They were often constructed as alley buildings, sharing a lot with as many as two larger tenement buildings."

This article goes on to state that these houses are unique to St. Louis (See above). This is one of about three still remaining in Fredericksburg-- located a few hundred miles southeast of St. Louis.