The city, built near the rebuilt Macross city was a major trading partner of it's neighbor.  Relatively new compared to other cities that survived the first Robotech war.  though it was nothing more than a small town during the first war.  Afterwords it was one of the few places that could keep humanity alive and with it's close proximity to New Macross city it flourished with many of humanities misplaced taking up residence there. 

After Kyron the insane crashed his space ship into the SDF-1 and SDF-2 causing Macross city to be uninhabitable.  Most of the population moved to monument city and so did the government and military.  The city seemed to almost triple over night and with it came many of the problems of a over crowded unprepared city.