Although there are several sources of traffic sign information available on the web, there are very few resources specifically focused on the history and chronology of sign designs. This site seeks to amend that, with a peek at the progression of American signs from 1927 to the present.
The date appearing below each sign is in most cases the earliest reference I've come across to it in the MUTCD...on occasion, sign designs may have been used by individual states for years before being officially codified. Likewise, many older sign designs remained in concurrent use after newer versions came about; particularly in regard to word-based warning signs.
The primary sources of reference for this site are copies of the Manual of Uniform Traffic Control Devices and predecessor documents; various revisions of which are viewable on Richard Moeur's and Gene Hawkins' websites. Graphics were created using a prosaic combination of PC Paintbrush and IrfanView, with debt owed to the TrueType incarnations of Mike Adams' Roadgeek Fonts. Most rectangular signs are shown to a similar scale, with square signs scaled to a common size.