| Business | Phone |
| Ibew 570 Pennsylvania Ave, Mason City 50401 | (641) 424-2940 |
| International Union-Engineers 510 S Pennsylvania Ave, Mason City 50401 | (641) 423-2630 |
| Public Professional & Mntnc 1911 S Carolina Ave, Mason City 50401 | (641) 424-6064 |
| Teamsters 404 15th St Nw, Mason City 50401 | (641) 424-3771 |
| United Steelworkers Of America 510 S Pennsylvania Ave, Mason City 50401 | (641) 424-8480 |