User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-65.128.179.225-20130825102505

Castiel told the story. They were the first creatures created by God, and he was so distraught by their behaviors and such he sealed them away in Purgatory. That being said they were created first to inhabit the Earth, before the angels were created and charged with watching over it.