The Wasteland, often referred to as "Haven County" is the last known pocket of surviving human life on earth. It encompasses Circuit Falls and it's surrounding cities such as Steelport and Nekropolis. It is also home to vast variety of mutants and monsters, known as Wastelanders.
The Wasteland was created by a massive nuclear war in 1964 that wiped out civilization across the entire earth. The massive fallout killed billions of biological beings, and mutated millions more. The wildlife that inhabit the Wasteland, and perhaps the entire outside world, were horribly mutated.
Many mutants were once human, or share a common ancestry with humanity, making them capable of sentience on a human level. These are the most dangerous and mysterious of the mutated creatures that wander the wastes.