Map of Emerging US Megaregions

The America 2050 organization deals in planning for future growth in the US, and they've put together this map of what the US will look like in 2050, entitled "The Emerging Megaregions." Essentially, they foresee the swelling megalopolises in several different areas of the country merging with each other to form giant conurbations.

They define them thus:
As metropolitan regions continued to expand throughout the second half of the 20th century their boundaries began to blur, creating a new scale of geography now known as the megaregion. Interlocking economic systems, shared natural resources and ecosystems, and common transportation systems link these population centers together...

Most of the nation's rapid population growth, and an even larger share of its economic expansion, is expected to occur in 10 or more emerging megaregions: large networks of metropolitan regions, each megaregion covering thousands of square miles and located in every part of the country.