Its grand opening—a major agricultural show on June 7, 1915, for which the local daily newspaper dedicated the entire front page to covering the event.

In 2008, a group of local businesspeople signed a deal to bring an NBA Development League team to the Expo, as well as to renovate the arena's facilities.

[4][5] It was confirmed, and the Expo Building is home to the Maine Red Claws, beginning play for the 2009–10 season.

[6] Over the years, many notable figures have appeared at the Expo, including Babe Ruth, Rudolph Valentino, Rocky Marciano, presidents John F. Kennedy[7][8] and Barack Obama,[9][10] and Paavo Nurmi.

It has hosted significant performances, including the first East Coast concert of the Beach Boys (1963), James Brown, Dolly Parton, Janis Joplin, Queen (1974), the 60th Anniversary Ball of the Portland Symphony Orchestra, world championship kickboxing, and gala banquets for the Senior's Pro Golf Tournaments featuring Arnold Palmer and Gary Player.