From Halopedia, the Halo wiki
In 2432, 70,003 colonists settled Meridian and established the first town of Avignon. As many of Meridian's settlers came from France on Earth, Avignon was named after the French commune of the same name.
When the Covenant invaded the world in 2548, during the Battle of Meridian, Avignon was not among the cities initially targeted by the Covenant. However, by early 2551, Meridian was lost to the United Nations Space Command and Avignon was likely glassed alongside most of the moon's surface and population centers.
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