
According to Southeast Michigan Council of Governments records, this building was built in 1920 and measures 1,200 square feet. At the time this was built, it was located along an interurban rail line connecting Royal Oak and Detroit, whose remnants are still reminded today with the grass median of this part of 4th Street.
The "disc" circular decor bookending the store sign seems to likely indicate this was once an A&P, but do you have any doubts on this ever being an A&P?