Looks like either a wild or bur cucumber - 2 different plants but with a very similar appearance. Both are native annuals and can grow to an impressive size in a single season - upto 20' and will cover whatever is in their path. August is their prime season, especially after a hot and wet summer.

Bur cucumber is apparently very common in southern MN. There are numerous recent online articles about them.

Thank you! It is taking over an area where we are planning to put in a large vegetable garden next year. The deer are bad enough without this problem :)

It looks rather close to tall trees. Maybe not the best spot for a vegetable garden?

There are trees to the east, north, and west, but completely open to all the south light it could ask for! The previous owners of this land had a large garden in this plot for many years. The problem we did discover this year, with a wet spring and that abundance of trees, was that it is peat ground, and likes to hold on to moisture.