How Obama signed the Hall of Fame guestbook yesterday http://t.co/fCHEYwcIL3@USATODAYpic.twitter.com/Pcw3gCfyzD

— Joseph Spector (@JoeSpectorNY) May 23, 2014

The most powerful man in the country isn’t above declaring his sports fandom.

On a trip to the Baseball National Hall of Fame and Museum in Cooperstown on Thursday, President Obama signed the guestbook, and after helpfully providing his address — 1600 Pennsylvania Ave., Washington, D.C. — made his baseball allegiance known. “Go Sox!,” he wrote, as in White Sox.

Obama became the first sitting president to visit the Hall, traveling to central New York to tout his administration’s plan to boost international tourism.