What may have continued over the centuries is a mystery until Victorian England in the 1880s. In The Hound of the Baskervilles by Sir Arthur Conan Doyle, Sherlock Holmes and Dr. Watson are found unsuccessfully trying to catch a public Hansom cab. Holmes, however, got close enough to the cab to spot its license number, which became a major clue in cracking the case.

As automobiles became more common in the late nineteenth and early twentieth century, a need for their registration arose. Prior to universal licensing at the state level, cities and counties issued their own license plates. Although actual plates were sometimes provided, more often than not these so-called pre-states were homemade -- commonly metal house numbers attached to a leather pad.

By action of its Legislature, New York became the first state to require vehicle registration as of April 25, 1901, and California followed suit later that year. The first New York issues were homemade plates, bearing the initials of the owner without any numbers. Massachusetts was the first state to actually issue plates, beginning in 1903. By 1918, all 48 of the contiguous United States were issuing license plate. Although they were territories at the time, Alaska and Hawaii began issuing plates in 1921 and 1922, respectively.

License plates have changed significantly over the years. Early plates were not fancy -- just the state name or abbreviation, a registration number, and, more often than not, the year. Fancy lettering, reflectorization, slogans, county names, illustrations or logos peculiar to a particular state became more common as time passed. Since the American Bicentennial, the states have begun issuing graphic plates having scenes, slogans, or elaborate devices silk-screened onto the plates. For many years plates had the numbers and letters embossed or stamped into the metal and painted. Now the trend is toward flat, unembossed plates.

Beginning in 1957, most types of North American plates have been a standard size, six by twelve inches. Prior to that, different sizes and shapes were not uncommon. Plates were normally rectangular, but oval, square, round, and triangular shapes were used. For a number of years, Kansas and Tennessee cut their plates to match the shaped of the state itself. The distinction for the most unusually shaped plates goes to Northwest Territories and Nunavut in Canada, which have their plates cut in the shape of a bear.

A wide variety of materials has been used for license plates. Metal is most commonly used, with steel and aluminum leading the way. Tin, copper, and brass have been used as well. Early plates for many states were porcelain covered steel, but these soon proved to be too expensive to produce in the quantity needed. Wood, rubber, pressed soybean meal, cardboard, and plastic have been used in lieu of metal or when metal supplies were limited, as was the case during World War II. Windshield stickers, or metal tabs or stickers attached to the plates themselves have been employed for the renewal of plates.