These are links to the UFCW UNION authorization process
Iowa
https://ufcw431.com/organizing
Wisconsin
http://www.ufcw1473.org/?zone=/unionactive/view_article.cfm&HomeID=107124&page=Join20Us
Minnesota
https://ufcw1189.org/node/524
Illinois/ South Dakota
http://www.ufcw1500.org/digitalauthorization
Missouri
http://www.ufcw655.org/organizing/
Kansas
http://www.ufcw.org/
Nebraska
http://www.ufcw1500.org/join-ufcw-1500
Hopefully all the links work for the particular state, if not they will at least lead in right direction.
Based on what is happening with hy-vee currently, this might be a good thing to look into.