Let's ignore reality and assume global warming doesn't exist and everything will stay about the same as it is now.

We're going to need to abandon:
Most of California (earthquakes, fires)
All of the Gulf Coast (hurricanes)
A substantial part of the Atlantic Coast (hurricanes. see Sandy)
All of Puerto Rico (hurricanes)
*All of the cities along the Lower Mississippi (flooding. there's going to be a levee breach sooner or later).

So we're down, at a minimum, Los Angeles, San Francisco, Santa Barbara, Houston, New Orleans, Puerto Rico, Mobile, Pensacola, Miami, Savannah, Charleston, Wilmington, and, apparently, Augusta, Kansas.