Chapter 9 follows the Canada–US border’s development from 1900 until the 1930s. It surveys the Alaska Boundary Survey, World War I, Prohibition, the Great Depression, and Indigenous resistance to new immigration laws. In the 1920s, the Indian Citizenship Act and National Origins Act extended federal immigration law over Indigenous people, resulting in resistance. Deskaheh (Levi General) gave speeches in Europe to garner support for the Haudenosaunee rights to self-governance. Clinton Rickard helped found the Indian Defense League of America to increase pan-Indigenous resistance to federal policy. Paul Diabo’s legal challenge to the Immigration Service’s interpretation of the Jay Treaty helped entrench Indigenous mobility as a fundamental part of the Canada–US border. As battles over citizenship and prohibition attested, increases in federal personnel did not give either country the ability to ignore popular resistance.