When was the first one installed in the US? And where?

It was installed in 1920 on the corner of Woodward and Michigan Avenues in Detroit.

http://www.ideafinder.com/history/inventions/story010.htm

I think someone may find a traffic signal that operated earlier than thios, but the question was traffic light. Whoever posts needs to make that distinction.

I see where you got that Jenny and I didn't know about that one..so thanks! But, there is another one if someone could come up with it?

The first electric traffic signal was installed in Cleveland, Ohio, in 1914. It consisted of a green and red light with a warning buzzer to indicate when the light was about to change.

The world’s first traffic light came into being before the automobile was in use, and traffic consisted only of pedestrians, buggies, and wagons. Installed at an intersection in London in 1868, it was a revolving lantern with red and green signals. Red meant "stop" and green meant "caution." The lantern, illuminated by gas, was turned by means of a lever at its base so that the appropriate light faced traffic

Gas-lit traffic signal, 1868: The first street crossing lights were erected in England in 1868. The lights, which gave red or green 'stop' or 'go' signs to traffic required a policman to operate them. Garrett Morgan's traffic signals improved on designs such as these.



In 1923, Garrett Morgan received a patent for his new concept (U.S. 1,475,024 issued in 1923) -- a traffic signal to regulate vehicle movement in city areas.
After witnessing a collision between an automobile and a horse-drawn carriage, Garrett Morgan took his turn at inventing a traffic signal. Other inventors had experimented with, marketed and even patented traffic signals, however, Garrett Morgan was one of the first to apply for and acquire a U.S. patent for an inexpensive to produce traffic signal.

The very first traffic light was a revolving gas lantern with red and green lights installed in a London intersection in 1868, before the advent of automobiles. A later version of the traffic light based on railroad signals was installed in Detroit, Michigan, in 1920.
from Yahoo

Lester Wire was born in September of 1887, and died in April, 1958. One of his greatest achievements was his invention of the electric traffic light, for which his name was placed in Who’s Who of America and he is known for world-wide. This first traffic light was a large wooden box with two six-inch holes on each side. Inside the holes were Mazda lamps which had been dipped in red or green watercolors. The box was painted yellow and planted on top of a ten-foot pole. The light was installed in Salt Lake City in 1912 at the intersection of Main Street and Second South. It was operated by a patrolman who used a two way throw switch to change the light’s colors. To power the light, wires from the box were attached to the overhead trolley wires.

[This message was edited by Doriangreyed on 09-14-03 at 11:24 AM.]

ok thanks Dorian and Jenny for the links to! Thats a great article on it.