The team began play in 2009 as the Milwaukee Iron, and competed in af2, the AFL's developmental league.

[2] The Iron played its first game on Thursday, March 12, 2009, a 60–0 exhibition shutout of the New Zealand Overstayers at the Bradley Center.

[3] They opened the regular season on Friday, March 27, 2009, when they played host to the Iowa Barnstormers.

The Mustangs were covered locally by WAUK (540 ESPN MILWAUKEE) and Time Warner Cable Sports 32.

On October 2, 2013, the AFL announced that an ownership group led by Portland businessman Terry W. Emmert has been approved by the AFL's board of directors to purchase a majority of the Milwaukee Mustangs and relocate the team to Portland, Oregon.