Starting in the 1940s, simple and economical Ranch style houses were mass-produced to meet the housing needs of returning WWII soldiers and their families. This style is characterized by a single story low pitched building, often with at least one picture window and a sliding glass door that opens to a patio. There is usually an attached garage, sometimes connected by a breezeway. Many of the structures lack detail and they became known for their plain, unadorned exteriors. Although Ranch style homes are traditionally one-story, Raised Ranch and Split Level Ranch homes have several levels of living space. The low horizontal elevations of Prairie Style houses pioneered by Frank Lloyd Wright and the informal Bungalow styles of the early 20th century paved the way for the popular Ranch style.