100,000 years ago, when the Skrulls, back then a benevolent race of aliens, held a competition for the inhabitants of the planet Hala, the Cotati and the Kree. The Skrulls held a competition in the Moon and created the Blue Area as its stage. When the Skrulls left for the to race to build something for them, the Kree created a city while the Cotati created an ecosystem. When the Skrulls returned to the Blue Area, they chose the Cotati as the winner for their creation. Upset by the results, the Kree killed the Cotati, stole the Skrull's ship and declared war on them, thus starting the Kree-Skrull War.
Some time later, Uatu the Watcher settled in the Blue Area of the Moon and even created a citadel to act as his home to observe the evolving humans.
The Blue Area is also the site where the Fantastic Four first fought the Red Ghost and where they also met Uatu for the first time.
When the Inhumans were finding a home suitable for them, they launched their city, Attilan and settled in the Blue Area, before leaving to go to Kree space.
This is also the place at the end of the Dark Phoenix saga, where Jean Grey committed suicide in order to prevent anymore unnecessary deaths caused by the Dark Phoenix.