Minnesota voters can register at the polls on election day. From the Voter Registration website:
Registering on Election Day
If you are not registered to vote or need to update your registration information, you may do so at your local polling location on Election Day. However, you are required to provide proof of residence when registering on Election Day.
To register at your polling place on Election Day, you must have one of the following with your current name and address in the precinct to verify your residence:
An employee of the residential facility where you live who can confirm your address with a signed oath