The Twenty-first reunion of the Society of the Army of the Potomac
Portland, Maine July 3, 1890
Chamberlain was president of the society the previous year in New Jersey and had helped to sway the vote for the next to be held in Maine, this is evidenced in Holman Melcher's speech on page 12.
Francis Walker's speech on page 18 is also worth a glance. Did Chamberlain possibly use this when composing his own speech "The Last Review of the Army of the Potomac