- Maxwell
- McCallsburg
- McCausland
- McClelland
- McIntire
- Moneek
- Mediapolis
- Melcher-Dallas
- Meservey
- Miles
- Mingo
- Missouri Valley
- Millrock
- Morse Island
- Modale
- Mondamin
- Moneta
- Metz
- Murphy
- Maharishi Vedic City
- Merrimac
- Montour
- Modern Manor Mobile Home Park
- Morning Sun
- Mount Ayr
- Moville
- Muscatine
- McGargels Ford
- Mink Island
- Mooar