After being seated mayor in 1914, Armstrong went on an unprecedented building spree in the city, earning him the affectionate nickname "Joe the builder" among voters. His classical structures still grace the city today, including the massive 10 story City-County Building taking up an entire city block. His rule as mayor was also responsible for massive construction projects that are not so easily visible such as the Armstrong Tunnel which for the first time allowed easy access from the Grant & Libertysection of downtown to the Southside neighborhood under the steep hill that Duquesne University sits on in the Bluff neighborhood.