Registration of Aliens, St. Paul
In February 1918, the Minnesota Commission of Public Safety required all "unnaturalized aliens" -- immigrants who were not US citizens -- to register with the state. Information such as their names, birthdates, places of birth, citizenships, and allegiances was collected. Three copies of the forms were completed and signed, to be distributed to the Justice Department, the State Capitol, and the local authorities (usually the sheriff). Xenophobia (fear of foreigners) was already common during this time and was especially severe towards German Americans. There was widespread fear that German immigrants would have some loyalty to the Kaiser and conspire against the US war effort, which led to this and other actions by the CPS.
The Iron Range Research Center has an online index of 1918 Alien Registrations from Minnesota. Choose "Alien Registration of 1918" in the Record Type dropdown menu.