Grand Canyon

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

Marvel The Transformers comics
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 was left alive.

Super-God Masterforce cartoon
Devil Z in the body of BlackZarak, along with Hydra and Buster launched their Devil Thunder attacks from the canyon. Ginrai and the Headmaster Juniors traveled there to confront the Decepticons. While Ginrai fought the two Decepticon Godmasters, the Juniors ended up battling Krakens and Sparkdash drones, and were aided by Wilder and Bullhorn. Ginrai, combined with Godbomber as God Ginrai, battled the Darkwings to a draw. Then Overlord arrived and fought at length with Ginrai while the other Autobots hunted for BlackZarak. Lightfoot and Road King got trapped in a cave, while the others encountered King Poseidon. With the help of Grand Maximus, Ginrai overcame Overlord long enough to join the others, but at that point the Decepticons pulled out anyway.

Armada cartoon
The Autobots were alerted to a Mini-Con panel activating at the Grand Canyon, and warped there. Meanwhile Megatron sent 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 were distracted, allowing Optimus Prime to recover the Mini-Con, who turned out to be his old partner Leader-1 Sparkplug.

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

Go-Bots cartoon
The Rattlesnake 500 Desert Road Rally, a race held near the Grand Canyon, was interrupted by the errant Go-Brillium test subjects Racer-Bot ALPHA and Racer-Bot BETA. They played havoc with the other drivers and the crowd before Aero-Bot, Hauler-Bot and their team arrived to stop the troublemakers.

Prime cartoon
At some point in the distant past, the Grand Canyon became the largest Cybertronian battlefield in the galaxy. When Megatron got his hands on some Dark Energon, he used it to raise a horde of Terrorcons from the corpses buried there. Optimus Prime and Ratchet were forced to fight them all. The Dark Energon chunk remained there until Megatron, in possession of Bumblebee's body, retrieved it.

Titan Prime comic
The latitude and longitude for the Grand Canyon were encoded in a copy of Invasionauts II purchased by Raf Esquivel. When he played the game, it hyponotised him and forced him to open the GroundBridge to those co-ordinates, at which point Vehicons started pouring through.

After kidnapping Air Force One, Starscream took it to the Grand Canyon, and left a ransom message on the black box to let the Autobots know to bring Optimus Prime bound and gagged. This merely resulted in the Autobots turning up in force and beating the tar out of Starscream and his Vehicons in order to rescue the President.