Spain in the U.S.

I'm aware that St. Augustine, Florida represents the earliest European city in the US (some qualifications to that), and the Southwest, which was originally Spanish, then Mexican, also had early settlements (not sure of the chronology) and that's all a correction to the idea that history begins at Plymouth Rock or Jamestown.

What I didn't realize was how far north the Spanish had come, and where they built forts--like 300 miles into North Carolina?

Which reminds me of Prof. Bailyn's most recent book, which looks at some of the lesser known strains of settlement on the East Coast.