Set in stone is supposed to mean immutable, but Luigi Del Bianco’s determined descendants just now appear to be winning the official affirmation that the Italian-American from Westchester County deserved long ago for shaping one of the nation’s most famous monuments.

“If being the chief carver at Mount Rushmore is not the American dream for an immigrant to these lands, what is?” said Douglas Gladstone, the author of the 2014 book, “Carving a Niche for Himself: The Untold Story of Luigi Del Bianco.”

Hundreds of workers finished sculpting the faces of four U.S. presidents (Washington, Jefferson, Theodore Roosevelt and Lincoln) into Rushmore’s granite southeast slope in the Black Hills of South Dakota 75 years ago. They toiled under the direction of Gutzon Borglum, the designer and chief engineer, and his son Lincoln, and their names are listed at the monument as part of a team effort.

But last month, the National Park Service finally recognized the singular contribution that Gutzon Borglum had long ago attributed to Del Bianco, who came from Naples, Italy, when he was 17 and eventually settled in Port Chester, New York.

On Facebook, the National Park Service posted this biography, which officially mentioned Del Bianco’s title for the first time: “Artist Luigi Del Bianco came to work at Mount Rushmore at the request of Gutzon Borglum, the designer and engineer of the stone sculpture. Luigi Del Bianco worked for Mr. Borglum during the seasons of 1933, 1935, 1936 and 1940. He was a Senior Driller until the end of July in 1935 when Mr. Borglum designated him Chief Carver.”

Cameron Sholly, the director of the Midwest region for the National Park Service, which includes South Dakota, said that when he assumed the position last year he began reassessing Del Bianco’s role at the request of the carver’s 53-year-old grandson Lou.

Correspondence provided by Lou Del Bianco, who lives in Port Chester, combined with research by park service historians, convinced Sholly that for whatever reason, Luigi Del Bianco’s contribution to the monument had been overlooked.

“He is worth any three men I could find in America, for this particular type of work,” Borglum wrote, in documents that Lou Del Bianco and an uncle, Caesar Del Bianco, discovered at the Library of Congress. “He is the only intelligent, efficient stone carver on the work who understands the language of the sculptor.”

Del Bianco was born in 1892 aboard a ship near Le Havre, France, as his parents were returning to Italy from the United States. Raised in Meduno, northeast of Venice, he studied stone carving in Vienna and Venice starting when he was 11. He immigrated to Vermont when a cousin wrote that skilled carvers were in demand there.

He returned to fight for Italy in World War I, went back to Vermont in 1920 and finally settled in Port Chester, where a fellow carver introduced him to Borglum, who hired him to work at his studio in North Stamford, Conn., as well as to his future wife, Nicoletta Cardarelli.

Del Bianco and Borglum worked together briefly on the Confederate Memorial on Stone Mountain in Georgia, and on the Wars of America Memorial in Newark, N.J. Del Bianco was a model for a number of the figures. In 1933, Del Bianco was recruited to Mount Rushmore, eventually as chief carver at $1.50 an hour, or $72 a week. (He quit twice when financing ran out.)

As chief carver, his priority was refining the facial expressions on the presidents’ 60-foot-high heads. He fixed a foot-deep crack in Jefferson’s lip with a patch and he sculpted Lincoln’s eyes, highlighting the pupils with wedge-shaped granite stones to reflect the light.

“I know every line and ridge, each small bump and all the details of that head so well,” he told The Herald Statesman of Yonkers in 1966.

In 1941, the elder Borglum died, financing dried up, plans to carve the torsos of the presidents to the waist were abandoned and Del Bianco returned to Port Chester, where his company carved hundreds of tombstones. He died in 1969 at 78 of silicosis, which is caused by inhaling dust from crushed stone.

“The doctors were amazed that he lived as long as he lived,” his daughter Gloria told National Public Radio in 2012, “because the dust in his lungs was like a rock.”

A campaign by Luigi’s son Caesar to rectify the official oversight began in the late 1980s after he read Rex Allen Smith’s “The Carving of Mount Rushmore,” in which his father’s role was ignored. Caesar, who died in 2009, enlisted his nephew Lou.

Gladstone, the author of “Carving a Niche for Himself,” said that was like writing about the Yankees without mentioning Joe DiMaggio.

“After years of being dismissive to the family, the agency at last did the right thing,” Gladstone said.

The recognition on Facebook was also welcomed by Joseph Scelsa, the founder and president of the Italian-American Museum in Manhattan.

“After 25 years, the National Park Service has finally acknowledged that Luigi Del Bianco was in fact the chief carver,” Lou Del Bianco said. “Permanent recognition at the mountain is what we are really after, but this is a breakthrough and a start in the right direction.”