Northern Mariana Islands befuddle me

As I watched the delegates chime in their votes for the Republican nominee last night the Northern Mariana Islands passed in order to let Arizona have the grand finale. The who? What? Huh? I have never claimed to be a political expert. Nor have I claimed to be a whiz in geography, but I did not know much about this little group of islands. I guess I should stick to being a financial guru, but I found this interesting.