There are people who argue that the 20th century in the United States really began nearly two decades after its formal start. That date is April 6, 1917. It’s not because our calendars were defective, but because on April 6, 1917, America entered World War I fighting on the side of France and the United Kingdom against the forces allied with Germany and Austria-Hungary.

The United States joined the conflict as a nation with limited experience on the world stage. It emerged as a major international power.

“It changed America’s role in the world,” said Jack Monahan of Essex, one of 12 members of the United States World War One Centennial Commission, charged with making sure Americans don’t forget the struggle.

The commission, Monahan explained, has a mandate to memorialize the war, honor those who fought in it and educate the wider public about the American role in the conflict. The group organized a major commemoration on the anniversary in Kansas City featuring a video narrated by actor Gary Sinise, along with music, poetry, and readings all designed to mark America’s entry into the war. The event included flyovers from a B-2 stealth bomber and a French aviation group, trailing red, white, and blue plumes to signify both the French and American flags.

The celebrations were held in Kansas City because there is an existing World War I memorial in that city, but part of the commission’s mandate is to help raise funds for a World War I memorial in Washington, D.C. The monument will be located in Pershing Park, named for General John Pershing, the commander of the American Expeditionary Forces.

Monahan, a retired U.S. Army officer, pointed out that there are monuments in Washington D.C., to the other major struggles in which the United States has participated in the 20th century: World War II, Korea, and Viet Nam, but no memorial structure to World War I. The commission is also charged with raising funds to renovate some 100 World War I memorials throughout the country.

World War I, Monahan said, is the least-known, the most overlooked of 20th-century conflicts, yet he maintained that much of what characterized that century grew from the war. The draft brought people who had come to this country in the great years of immigration at the end of the 19th and the start of the 20th century together for the first time. Monahan pointed out that the famous 42nd Infantry Division known as the Rainbow Division had National Guard units from more than 26 states.

“In that sense, it made modern America,” Monahan said.

It was, however, not a rainbow in one respect: It rejected a black New York unit with the words “black is not a color of the rainbow.” The United States Army was segregated and black units fought only under French command.

World War I set the stage for modern combat in both its slaughter and its technology. The Meuse-Argonne offensive, from September to November of 1918, involved more than 1.2 million American soldiers and took a total of more than 26,000 American lives, still more than in any other battle ever fought by this nation’s troops.

It was the first conflict in which tanks were used and the first in which airplanes on both sides fought battles in the sky. One of the German air aces, Manfred von Richthofen, better known as the Red Baron, became an ongoing figure in Charles Schulz Peanuts comic strip, the antagonist against whom Snoopy dreams of fighting imaginary air battles.

The war inspired songs, some like “Over There” with its famous refrain “The Yanks are coming,” by George M. Cohan that became a part of the American songbook. But there were others that came and went, like a 1918 hit called, “If He Can Fight Like He Can Love, Good Night Germany!”

The World War I Centennial Commission has a website that details educational and commemorative programs, historical information and provides a place for individuals to recount memories that have lived in their own families of World War I.

The Connecticut State Library also has a website, Connecticut in World War I, with stories and photographs of Connecticut solders and life in Connecticut on the home front, lists of events and lectures around the state, and information on the library’s digitization program. There are digitization days around the state where residents can bring World War I memorabilia that will be digitized for the state library’s collection. Suitable objects include photographs, journals, discharge papers, flags, banners, and posters. There is a complete list at the Connecticut in World War I website: ctinworldwar1.org.

Along with the image, those who bring artifacts have a chance to tell the story behind the object and the family memories it represents.

There is a digitization day in Middletown on Thursday, April 27 from 3 to 7 p.m. at the Russell Library located at 123 Broad Street.

For information on digitization days and Connecticut in World War I, visit ctinworldwar1.org. For information on the national celebration of the World War I Centennial, visit www.worldwar1centennial.org.