State where the first traffic light was installed (4)

I believe the answer is:

ohio

(Other definitions for ohio that I've seen before include "State of the union" , "part of the Midwest!" , "state of America" , "Midwestern US state and river" , "State of east central US" .)

I've seen this clue in the Universal.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.