The first electric headlamps were introduced in 1898 on the Columbia Electric Car, from the Electric Vehicle Company of Hartford, Connecticut, and were optional.  Peerless made electric headlamps standard equipment on their 1908 model’s, becoming the first gas powered automobile company to light the way.  In 1912, Cadillac integrated their vehicle’s with “Delco electrical ignition and lighting system”, creating the modern vehicle electrical system.

“Dipping” (low beam) headlamps were introduced in 1915 by the Guide Lamp Company, but the 1917 Cadillac system allowed the light to be dipped with a lever inside the car rather than requiring the driver to stop and get out.  In 1927, the foot-operated dimmer switch or dip switch was introduced and became standard for much of the century.   1933–34 Packard’s were equipped with tri-beam headlamps, the bulbs having three filaments.  From highest to lowest, the beams were called “country passing”, “country driving” and “city driving”.  The 1934 Nash also used a three-beam system, although in this case, the bulbs were conventional two-filament type, and the intermediate beam combined low beam on the driver’s side with high beam on the passenger’s side, so as to maximize the view of the roadside while minimizing glare toward oncoming traffic.

The last vehicles with a foot-operated dimmer switch were the 1991 Ford F-Series and E-Series [Econoline] vans.

The standardized 7-inch round sealed beam headlamp was introduced in 1940, and was soon required (exactly two per car), for all vehicles sold in the United States, freezing usable lighting technology in place until the 1957, for Americans.  Because the law was written to prevent “bad headlights,” it by design looked backward, and was historically unable to deal with improved innovative designs. In 1957, the law changed slightly, permitting Americans to possess vehicles with four 5.75-inch round sealed beam headlamps, and in 1974, these lights were permitted to be rectangular as well.

In 1967, the U.S. federal Department of Transportation was created and in 1968 they created the Federal Motor Vehicle Safety Standard 108, which governs “Lamps, reflective devices and associated equipment”.  This is the current governing body for the American Automobile manufacturers.

Source of information – Wiki