Maine marked the 100th Anniversary of its Statehood with the Maine Centennial Exposition, a celebration in Portland, Maine from June 26, 1920 to July 5, 1920. The Exposition was held, primarily, in the Portland Exposition Building.
Per the
Official Program for the celebration, the Exposition's purpose was to "show goods made and sold in the State of Maine; to foster unity of purpose among business men; to build up, strengthen and aid the industrial and agricultural interests, as well as develop Maine's wonderful resources." The Exposition was sponsored by the Maine State Chamber of Commerce and Agricultural League.
The Exposition featured themed days throughout its run, including "Historical Day," "Music Festival Day," "Exposition Day," "Civic Parade Day," "State of Maine Day," "Maine Women's Day," "Mardi Gras Night," "Veteran Fireman's Day," "Church Services Day" and "Independence Day."
The week-long celebration included multiple parades, a variety of music concerts/performances, fireworks, luncheons, historical programs, sporting events, visiting warships, visiting airplanes, an Art Exhibit and a special "State of Maine" movie. A highlight of the event was the "Indian Village" which was a temporary encampment of Passamaquoddy and Penobscot Native Americans at Deering Oaks (a park in Portland; the park remains to the present day). The Exposition was definitely a smaller, more low-key affair vs. the Louisiana Purchase Exposition or the Panama-Pacific International Exposition.
The enabling legislation for the Maine Statehood coin was signed into law on May 10, 1920 by US President Woodrow Wilson; the bill calling for the coin was introduced in the House of Representatives on February 11, 1920. The less than two months time between when the coin was signed into law and the start of the Maine Centennial Exposition did not allow for the coin to go through the full process of coinage (i.e., design development, design approval, model preparation, die creation, coin striking) and be delivered to the Exposition organizers before the Exposition.
The Mint struck 50,028 (including 28 assay coins) of the authorized 100,000 coins in the late August/September time frame. Initial sales at $1.00 per coin were robust - approximately 30,000 were sold - even though the Centennial Exposition had closed, but then slowed dramatically soon after; the balance of the authorization was not requested. The Office of Maine's State Treasurer continued to have half dollars available for years after the Centennial (vs. returning coins to the Mint to be melted).
Would the Maine Half Dollar have enjoyed greater sales if it had been available in time for the Centennial Exposition? It seems likely, but difficult to say to what extent. 10% more? 20% more? Casual souvenir purchases by Exposition visitors would almost assuredly have bumped up sales. Strong sales at the Exposition might even have spurred a request for the balance of the coin's authorized mintage - creating 100,000 coins vs. 50,000 in the marketplace. But that is all mere speculation and collectors must make themselves content with the 50,000 examples available.
1920 Maine Statehood Centennial Half Dollar

For other of my posts about commemorative coins and medals, including more on the Maine Centennial coins, see:
Commems Collection.Of specific relation to the current post:
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1920 Maine Statehood Centennial - Revisited