For purposes of this chapter, the downtown business district of the City of Reed City shall consist of that area bounded on the north by the alley running east and west between North Chestnut and North Park, on the south by the alley running east and west between South Chestnut and South Park, on the east by White Pine Trail and on the west by the west lot line of the United States Post Office located at 232 West Upton Avenue, which line shall extend to the north side of the said Upton-Franklin alley and the south side of the Upton-Slosson alley, also including those portions of Chestnut and Higbee Streets contained therein, all within the City of Reed City, Michigan.