White, Steve. Saint Antony's Fire
Divergence: 1513 CE
What if: When he discovered Florida, Juan Ponce de Leon also discovered a crashed spaceship and a gateway between worlds.
Summary: After the Spanish Armada conquers England with advanced weapons and Queen Elizabeth flees to Virginia, our heroes learn the fate of the Roanoke colonists and of an alien plot to conquer Earth.
Comments: The dust jacket of the first edition abbreviates the title as St. Antony's Fire.
Published: Baen 2008 (1416555986BUY), 2009 (1439133298BUY).