Mississippi Valley Mayhem is excited to present a weekend full of Division 3 Women’s Flat-Track ROLLER DERBY in La Crosse! Dead River Derby (Marquette, MI), Bisman Bombshellz (Mandan, ND), MedCity Mafia (Rochester, MN) and of course your very own Mayhem will compete July 13-14 at the Onalaska Omni Center. Saturday, July 13 Doors open at ...