History was made on Tuesday, May 4, 1948, when the Mustangs and Salt Lake City Bees played the first game of organized professional baseball ever to be staged in Billings. Billings Mayor H.E. Biddinger threw out the ceremonial first pitch in front of 3,280 fans who braved near freezing temperatures. Gene Brocker's long double in the ninth inning scored Kenny Jensen from first base, providing the visitors from Salt Lake City with a narrow, 3-2, victory and spoiling the Mustangs home opener.
The Mustangs finished that inaugural season in last place. But the next season they finished second and made the playoffs. In 1964, the league was downgraded to short-season rookie league status and Billings dropped out of the Pioneer League. The Mustangs returned to the league in 1969 and won back-to-back championships in 1972 and '73. In all, the Mustangs have won 15 Pioneer League titles, more than any other team in the Pioneer League. The last championship came in 2014, with field manager Dick Schofield leading the club.
The 2020 season will mark the 47th consecutive year the Mustangs have been affiliated with the Cincinnati Reds, one of the longest running player development relationships in professional baseball. As the Cincinnati Reds start the 2020 season, seventeen former Mustangs are on the Major League 40-Man roster: Joey Votto, Tucker Barnhart, Amir Garrett, Jesse Winker, Tyler Mahle Alex Blandino, Robert Stephenson, Sal Romano, Phillip Ervin, Tejay Antone, Ryan Hendrix, Joel Kuhnel, Tony Santillan, Tyler Stephenson, Aristides Aquino, Nick Senzel, & Jose Siri.
Other current Major League players who wore a Mustangs uniform include Jay Bruce. Edwin Encarnacion, Todd Frazier, Justin Turner, Miguel Rojas, Billy Hamilton, Tanner Rainey, Shed Long, Brian O'Grady, Seth Mejias-Brean, and Didi Gregorius.
Other notable alumni include: George Brett, Paul O'Neill, Trevor Hoffman, Tom Browning, Adam Dunn, Ron Oester, Gary Redus, Dick Stuart, Kurt Stillwell, Gorman Thomas, Reggie Sanders, Skeeter Barnes, Scott Williamson, Al Cowens, Kal Daniels, Rob Dibble, Lenny Harris, Ruppert Jones, Larry Rothschild, Larry Shepard, Scott Sullivan, Nick Esasky, Eddie Milner, Jamie Quirk, Eddie Taubensee, Jeff Montgomery, Joe Oliver, Jack Armstrong, Tom Foley, Butch Henry, Jim Hickman, Reggie Jefferson, Don Wakamatsu, Keith Lockhart, B.J. Ryan, Ben Broussard, Aaron Boone, Paul Bako, Ray King, Danny Tartabull, Jason LaRue, Craig Tatum, Chris Dickerson, Enerio Del Rosario, Marcus Mateo, Dewayne Wise, Austin Kearns, Todd Coffey, Chris Valaiki, Corky Miller, Josh Roenicke, Logan Ondrusek, Sam LeCure, Curtis Partch, Juan Francisco, Scott Carroll, Dave Sappelt, Donald Lutz, Carlos Contreras, Daniel Corcino, Yorman Rodriguez, Jon Moscot, Neftali Soto, Drew Stubbs, Travis Wood, Adam Rosales, Chris Heisey, Josh Ravin, Zack Weiss, Ben Lively, Jose Lopez, Blake Trahan, Jimmy Herget, Tony Cingrani, Paul Janish, and Steve Selsky.