Veterans of the 42nd U.S. Infantry Division will return to Garden City on Saturday, 100 years after their forebears in the famous “Rainbow Division” marched through the village’s Camp Mills for the first time during World War I.

Ahead of the centennial celebration, the village has restored its Rainbow Monument at Saint James Street South and Clinton Road, which includes inscriptions listing the National Guard regiments from 26 states and the District of Columbia that made up the 27,000-man division.

The division earned its nickname when Douglas MacArthur, who then served as its chief of staff, remarked that its troops hailed from hometowns that stretched across the country “like a rainbow.”

The first soldiers began arriving at Camp Mills, a new tent camp that covered roughly a square mile over the southeastern corner of Garden City and part of Hempstead Village, in mid-August 1917, according to Paul Fanning, a retired New York National Guard lieutenant colonel and the memorials officer for the Rainbow Division Veterans Memorial Foundation.

“The nation’s first, quote-unquote, All-American division” came together then for the first time, said Fanning, who will preside over Saturday’s ceremony.

The soldiers — wearing rainbow patches originally sewn by Hempstead seamstresses — would pass through Camp Albert L. Mills, named for a New York native and Medal of Honor winner during the Spanish-American War, for training, and go on to fight in France.

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Nearly 3,000 of them were killed in action and more than 13,000 were wounded during World War I, according to the Garden City monument’s inscription.

When the war ended in 1918, “many troops came back through Camp Mills to be discharged,” local historian and Vietnam veteran Cyril Smith said.

In all, more than 200,000 troops passed through Camp Mills, Smith said — including poet Joyce Kilmer and writer F. Scott Fitzgerald, who mentioned the camp in his 1922 book, “The Beautiful and Damned.”

The camp closed in 1919 and the monument was erected in 1941, Garden City Village historian Bill Bellmer said. The 42nd U.S. Infantry Division is now part of the New York Army National Guard based in Troy.

“People tend to forget what went on 100 years ago,” Bellmer said.

The village has restored the monument “to bring out the original details,” including buglers and colorful rainbows across the top, Mayor Brian Daughney said. “It was a big part of the village back in the day.”

Sprung Monuments, which has locations in Lindenhurst, West Babylon, Elmont and Hackensack, New Jersey, restored the granite monument this summer, cleaning and repainting the reliefs by hand for just under $10,000. The Rainbow Division Veterans Memorial Foundation is to pay for half the cost, according to Village Administrator Ralph Suozzi.

“It just looked like a gray obelisk and now it’s come to life,” Village Superintendent of Public Works Joseph DiFrancisco said.