Four years after the North Siders struck gold, these were first installed in the United States in Salt Lake City. The first with three colors didn't happen until 1920 Detroit. (edited at 4:34 pm, October 24, 2016 (EDT))
Original question: Four years after the North Siders struck gold, these were first installed in the United States in Salt Lake City for the first time. The first with three colors didn't happen until 1920 Detroit.
traffic lights (signals ... stoplights)