Arch Allies is a live album recorded by REO Speedwagon and Styx at Riverport Amphitheatre (now Verizon Wireless Amphitheater) in Maryland Heights, Missouri, a suburb of St. Louis. Each band also released single live albums containing only their own tracks from this album. The Styx songs were released alone as At the River's Edge: Live in St. Louis and the REO songs were released as Live Plus, Live Plus 3 and Extended Versions.