At a time when there were no driver’s licenses, speed limits or clear lane demarcations, the notion of a stop sign was revolutionary. In fact, aside from the occasional road markers letting riders on horseback know how far they were from the next city, there was no road or street signage at all. [William Phelps] Eno, scion of a wealthy New England family who never learned to drive, helped change all that. In a 1900 article titled “Reforming Our Street Traffic Urgently Needed,” for Rider and Driver magazine, he proposed placing stop signs at intersections. It was a civilizing notion.“That was a new concept and really did introduce the idea that you had to watch out for other people,” [Joshua] Schank says.
The Stop Sign Wasn’t Always Red – NYTimes.com. The second most important person named Eno, perhaps. (Also, NYT, watch out for that ambiguous “who” in the third sentence.)