The U.S. Manual on Uniform Traffic Control Devices was first published in 1935.
The manual grew out of an effort to make traffic signs, signals, and pavement markings consistent across the United States. Before it appeared, AASHO had published a rural-highway manual in 1927, while the National Conference on Street and Highway Safety issued guidance for urban streets in 1930.
A joint committee representing those organizations developed the first national MUTCD. That history explains a common mix-up: 1927 and 1930 refer to important predecessor manuals, not the first MUTCD itself. The Federal Highway Administration has administered the manual since the 1971 edition, although earlier federal agencies helped develop and publish revisions.
The MUTCD remains the national standard for traffic-control devices on public roads. Its purpose is uniformity: a stop sign, lane marking, warning symbol, or signal should communicate the same basic message wherever drivers encounter it.