This American style originated in homes built by German, or "Deutsch" settlers in Pennsylvania as early as the 1600s. A hallmark of the style is a broad gambrel roof with flaring eaves that extend over the porches, creating a barn-like effect. Early homes were a single room, and additions were added to each end, creating a distinctive linear floor plan. End walls are generally of stone, and the chimney is usually located on one or both ends. Double-hung sash windows with outward swinging wood casements, dormers with shed-like overhangs, and a central Dutch double doorway are also common. The double door, which is divided horizontally, was once used to keep livestock out of the home while allowing light and air to filter through the open top. The style enjoyed a revival during the first three decades of the 20th century as the country looked back with nostalgia to its colonial past.