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The History of the Stop SignStop signs originated in Michigan in 1915. The first had black letters on a white background and were somewhat smaller than the modern one. As they became more widespread, a committee supported by the American Association of State Highway Officials met in 1922 to standardize them, and it selected the octagonal shape that has been used in the United States ever since. The unique eight-sided shape of the sign allows drivers facing the back of the sign to identify that oncoming drivers have a stop sign and prevent confusion with other traffic signs.
In 1924, the sign changed to black on yellow, the predominant color scheme until 1954. Another competing group simultaneously advocated an even smaller, red-on-yellow stop sign. All of these signs were typically mounted only two or three feet above the ground.
The stop sign was altered eight times between 1935 and 1971, mostly dealing with its reflectorization and its mounting height; the most drastic change came in 1954, when the sign gained its white-on-red color. Red is also the color for stop on traffic signals, unifying red as a stop signal for drivers worldwide.
Although already widespread, use of the stop sign passed into law in the United States in 1966. They were later adopted by the UN Economic Commission for Europe as part of its effort to standardize road travel across member countries.