Bo-Wash Metroplex (NE-VA)
3/4 of the East Coast has merged into one single super district call the Bo-Wash Metroplex. The train systems of major cities of the past grew along with the cities themselves absorbed more and more of the surrounding towns, cities, and protected land. Eventual corporate blights spread until they merged into a single mega district with massive transportation system that worms its way throughout the entire Eastcoast.
A sea wall is erected around the Bo-Wash Runs from northern Appalachian Mountains around the NE tip of the form United States, meanders down the Eastcoast before turning inland just north of the old Virgina border and completes it's circuit in southern Appalacia. The massive walls are home to the lowest of the low-income residential districts that anyone with the creds to stay out of it refers to as the Debter's Prison.