Common law marriage does not apply in Minnesota (nor in most other states).
>is a form of irregular marriage that survives only in eight U.S. states and the District of Columbia; plus two other states that recognise domestic common law marriage after the fact for limited purposes.
>It has been gradually abolished in Western nation states since the sixteenth century, when the Council of Trent in 1563 ruled that no marriage thenceforth would be valid in the eyes of the Roman Catholic Church unless it were solemnised by a priest.
https://en.wikipedia.org/wiki/Common-law_marriage_in_the_United_States
http://www.ncsl.org/research/human-services/common-law-marriage.aspx