North Main Street has long been Union City's commercial hub, and the architecture of the Main Street business district and the residential area to the west, including much of West High Street, South Street, and the Avenues, led to the Union City Borough Historic District being placed on the National Register of Historic Places in 1990. Built primarily between 1865 and 1925, the district includes a wide sampling of late 19th-century eclectic and early 20th-century revival styles. Most of downtown's historic buildings are two to three stories tall, built of brick, and follow the two-part commercial block form common to small-town main streets in the mid to late 19th century, with a public commercial first floor and more private upper floors, a development that grew from the earlier shop-house building. Two buildings on Main Street showed more exotic architecture: the ca. 1880 building at 39 N. Main St., with Victorian influences such as a dentiled cornice, decorative stone window eyebrows, and a dentiled string course, and the 1889 I.O.O.F. building at Main and Market streets, with a scalloped stamped-metal cornice and parapet. Another significant building was the Cooper Opera House, which opened in 1873 at the northeast corner of Main Street and High Street, hosted road shows and later silent motion pictures, and featured nightly music from a large phonograph on its upper front balcony and Thursday-night performances by the local Coleman Band before it was razed in the early 1920s.