Power windows or electric windows are automobile windows which can be raised and lowered by pressing a button or switch, as opposed to using a crank handle. History Packard had introduced hydraulic window lifts (power windows) in fall of 1940, for its new 1941 Packard 180 series cars. This was a hydro-electric system. In 1941, the Ford Motor Company followed with the first power windows on the Lincoln Custom (only the limousine and seven-passenger sedans). Cadillac had a straight-electric divider window (but not side windows) on their series 75. Power assists originated in the need and desire to move convertible body-style tops up and down by some means other than human effort. The earliest power assists were vacuum-operated and were offered on Chrysler Corporation vehicles, particularly the low-cost Plymouth convertibles in the late 1930s. Shortly before World War II, General Motors developed a central hydraulic pump for working convertible tops. This system was introduced on 1942 convertibles built by GM. Previously, GM had used a vacuum system which did not have the power to handle increasingly larger and complex (four side-windows vs. only two) convertible top mechanisms. Chief Engineer of the Buick Division, Charles A. Chayne, "...had introduced an electrically controlled hydraulic system into the 1946 Buick convertibles that provided fingertip operation of the top, door windows, and front seat adjustment". These systems were based on major hydraulic advances made in military weapons in preparation for World War II. The "Hydro-Electric" system (windows, front seat adjustment and convertible top) was standard on 1947 model year. The seat and window assist system became available on GM closed cars (standard on some Cadillac Series 75 models and all Series 60 Specials, commonly called "Fleetwood" beginning with the 1948). The full system was standard only on the high-end GM convertibles made by Oldsmobile, Buick, and Cadillac. It was only available as a package; that is, power assisted windows, front seat, and convertible top (where applicable). This feature can be identified in 1948 and later General Motors model numbers with an "X" at the end, such as the 1951 Cadillac Sixty Special sedan, model 6019X. The electrically operated hydraulic pump system was shared by Hudson and Packard for their 1948 through 1950 models. The driver's door contained four buttons in addition to the remaining individual windows. Ford also had a similar electro-hydraulic system on higher-end convertibles. Mercury and Ford Sportsman convertibles (with wood trim)