The Pioneer Building is a seven-story office building in the Sullivanesque style located in downtown Oklahoma City. Originally built in 1907 as the home office for Pioneer Telephone Company, and on the National Register, this William Wells-designed building was constructed of gray marble terracotta with hand-carved details around both ground floor entrances and had fallen into disrepair after years of neglect.

Gardner oversaw the historic tax credit process and the meticulous restoration of the building shell which included the ground floor lobby, new storefronts on the first floor, and marble restoration throughout the building. Balancing bringing the building to code without compromising the exacting design intent of each floor proved particularly challenging on the Downtown Oklahoma City site.

Infrastructure improvements included re-establishing missing elevators and restoration of elevator cages, removal of blue granite covering the ground floor storefronts, and sidewalk repairs. Tenant improvements were also completed for corporate office spaces on three floors.