Body-on-frame is an automobile construction technology. Mounting a separate body to a rigid frame that supports the drivetrain was the original method of building automobiles, and its use continues to this day. The original frames were made of wood (commonly ash), but steel ladder frames became common in the 1930s. The Lincoln Town Car dominates the American limousine market because it is the last American luxury car made with body-on-frame, and therefore easily lengthened for livery work.