"The terra-formed world of Gridiron is a heavily fortified IMC stronghold, with many industries serving the corporation's defensive needs. The planet's population has soared to 90 million, yet Gridiron still contains large swaths of desert perfectly suited for military research., conducted far from prying eyes. " - The Art of Titanfall description for Training Ground
Gridiron is a planet on the Frontier. It is a habitable world with a population of 90 million, and is home to the IMC Training Ground known as Whitehead and an abandoned IMC Reservoir. Additionally, the planet's sunlight can be extremely deadly to those who stay in it for too long, hinting that the planet has an extremely weak magnetic field or ozone layer - if so, it is unknown how the planet is able to sustain 90 million people, or how Pilots are able to train in the sunlight less than 100 miles away.
The status of the reservoir suggests the planet's settlements are experiencing severe drought.
Gridiron is home to the aplty-named Gridiron Transport Services, a company that is responsible for manufacturing many of the cars seen on the Frontier.