Residents of the San Francisco Bay Area have noticed strange events and behavior around them since 2014. Though conspiracy theorists had their suspicions about these events and strange occurrences, it wasn't until four years later that some of those theories were revealed to be true: comic books have come to life, superheroes and supervillains live amongst the people, and they no longer need to live secret lives if they so choose.
For four years, Boston, Massachusetts was a hub of underground superhuman activity. Supers lived their civilian lives day in and day out, but one week out of each month, Boston would be at the mercy of superhumans and the Big Bads in charge. At the end of the week, all of that damage was wiped clean. This happened monthly for four years. In August 2018, all of that changed.
With a snap of Thanos' fingers, Boston's underground population of supers and their loved ones mysteriously vanished, only to reappear in the San Francisco Bay Area as if they had always lived there. Somehow, along the way, civilians were suddenly made aware of superhumans and that they live amongst them. Welcome to skylines.