Grand Canyon

The Grand Canyon is a steep-sided gorge in Arizona. Several events in the various Transformer wars have taken place there.

Fiction

Marvel Comics continuity

While filming the finale of Monster from Mars at the Grand Canyon under director Rollie Friendly, Skullgrin was ambushed and attacked by Circuit Breaker. Thanks to the avarice of Rollie, and the kindness of Carissa Carr, Skullgrin is left alive. Monstercon from Mars!

Japanese cartoon continuity

Super-God Masterforce continuity

Devil Z in the body of BlackZarak, along with Hydra and Buster are based in the Canyon and are launching their Devil Thunder attacks. Ginrai and the Headmaster Juniors confront the Decepticons. The Juniors have to fight off Krakens and Sparkdash drones, but are aided by Wilder & Bullhorn. Godbomber arrives and combines with Ginrai to form God Ginrai and help battle the Darkwings to a draw. Then Overlord descends from the skies... Battle to the Death!! God Ginrai VS Darkwings Reborn

Unicron Trilogy

Armada Cartoon continuity

The Autobots are alerted to a Mini-Con panel activating at the Grand Canyon, and warp there, while Megatron sends Cyclonus and Demolishor to recover the panel, with Starscream also traveling to the Grand Canyon, despite having no orders too. Thanks to a timely intervention from Perceptor the Decepticons are distracted, allowing Optimus Prime to recover the Mini-Con, who turns out to be his old partner Leader-1 Sparkplug Comrade

The canyon in this episode is referred to as "Big Canyon", but that's clearly an Engrish version of "Grand Canyon"