Over two centuries of shared border history, the Canada-United States border crossing experience has constantly evolved and been transformed through domestic political practices and international events. The border, as it has in the post-9/11 era, will (and is) necessarily be redefined in a post-COVID-19 world. Indeed, in 2020, the combination of a pandemic and the lack of health coordination at the continental level placed the border back at the heart of the debate, becoming the national health bulwark at the expense of states’ international obligations towards asylum seekers and refugees. The rapid closure of borders, has trapped many people on the move (tourists, seasonal migrants, snowbirds, refugees, displaced persons) outside their national territory or area of residence, thus underlining the fragility of all mobility. This evolution of global borders is decisive for the Québec-American relationship, articulated in recent times around a certain idea of a fluid border demarcation line. In recent times the Québec-U.S. border has changed substantially: This chapter will show that not only did the pandemic episode confirm an evolution that was initiated on September 11, but it also paved the way for an inevitable hardening of this part of the border.