Ironman
https://www.ironman.com/races
Revolution 3 Triathlon
https://rev3tri.com/
French Creek Racing
https://www.frenchcreekracing.com Open water swims including near Thurmont/Cunningham Falls
Racine Multisports
www.racinemultisports.com Multisport, running and open water swim races in MD & VA
Others
Additional websites to find races:
For more information on USAT events and membership: