Prior to stardate 5371, a Federation colony was established on this planet. It was the most remote inhabited planet in the Federation, lying at the outer fringe of the galaxy. Mantilles was home to 82 million people, and was governed by retired Starfleet commodore Robert Wesley.
Mantilles came under threat by an unknown cosmic cloud creature. Governor Wesley's attitude prevented planet-wide panic, and five thousand children were successfully evacuated before the cloud reached the planet. The crew of the Enterprise managed to stop the creature before it consumed Mantilles. (TAS: "One of Our Planets Is Missing")
In 2293, the location of Mantilles in the Milky Way Galaxy was labeled in a star chart that was in Captain James T. Kirk's quarters aboard the USS Enterprise-A. (Star Trek VI: The Undiscovered Country, production art)