As the main street for South Pueblo, Union Avenue is lined with exuberantly styled two-and three-story retail stores and offices. A 1921 flood inundated the Union Avenue area, destroying or damaging many structures. Of eighty-seven survivors in the district, seventy have been listed as contributing from an architectural and historical viewpoint.

Along Union Avenue are several pressed metal fronts, including one with a notable Schlitz logo atop the Schlitz Beer Hall (c. 1880), 223 South Union. Elaborate Italianate buildings at 222 South Union (1881) and 226–228 South Union (1887) have been spruced up. The Gold Dust Block, 130 South Union (at D Street), is an elegantly restored three-story brick mortuary close to the site of an old hanging tree. The McLaughlin Building, 330 South Union (at B Street), serves as a large, imposing cornerstone for the district.