1901
- Maine Historical Society opens the Wadsworth–Longfellow House as a historic house museum and begins construction of a library-headquarters building in Portland
1917
- The first Navy-built submarine, the L–8, is launched at the Portsmouth Naval Shipyard in Kittery
- Edna St. Vincent Millay (1892–1950) of Rockland publishes Renascence and Other Poems, for which she wins a Pulitzer Prize in 1923
1919
- Lafayette National Park, now Acadia National Park, is established on Mount Desert Island through the efforts of conservationist George B. Dorr, philanthropist John D. Rockefeller and others
1922
- Edwin Arlington Robinson (1869–1935) of Head Tide is the first Maine native to win a Pulitzer Prize, for Collected Poems
1924
- Mirroring a national trend, membership in the Ku Klux Klan rises in Maine. The Klan opposed increased immigration and protested the presence of ethnic immigrants, including those of the Roman Catholic faith in Maine
1929
- Great Depression begins, leading to farm losses, closure of some mills and factories, reduced incomes for many, and some bank closures in the state
1930
- Kenneth Roberts (1885–1957) of Kennebunkport, completes Arundel: A Chronicle of the Province of Maine and of the Secret Expedition Against Quebec, the first of many historical novels about Maine for which he wins a Pulitzer Prize in 1957
1931
- Former Governor Percival Baxter (1876–1969) donates 5,760 acres of land, including Mt. Katahdin, to form a the basis of a vast new state park, land he designates a "forever wild"
1934
- Maine's prohibition of the manufacture and sale of alcohol, first passed in 1851, is repealed a year after the repeal of the Volstead Act, which imposed national prohibition in 1919
1936
- Disastrous spring floods throughout Maine and the east coast result in losses totaling $25 million in the state
1937
- State offers free hunting and fishing licenses to Penobscot and Passamaquoddy Indian tribes, recognizing their aboriginal rights to hunt and fish in Maine
- Three–month strike by hundreds of shoe workers in Lewiston-Auburn closes or cripples 19 shoe factories
1944
- Prisoner of War camp is established in Houlton to house German POWS
1946
- Skowhegan School of Painting and Sculpture is founded, one of a number of artists colonies that thrived in Maine in the post–war years
1947
- During the "year that Maine burned," major forest fires sweep Mount Desert Island and other parts of the state, destroying more than 200,000 acres, 851 permanent homes, and 397 seasonal cottages
- The Maine Turnpike opens from Kittery to South Portland, making the state much more accessible to auto tourism. In 1955, it is extended to Augusta
1948
- Margaret Chase Smith (1897–1995) of Skowhegan and Lucia Cormier run in the nation's first all-female race for the U.S. Senate. Smith wins, making her the first Maine woman elected to the U.S. Senate in her own right and the first woman to serve in both houses of Congress
- Maine summer resident Andrew Wyeth (1917– ) paints "Christina's World," often cited as a defining image of Maine
