Daniel Chester French took Potter on as an assistant in 1883. While sculpting animals, he also worked as a manager and salesman in the marble quarries. From 1887 to 1889, Potter studied sculpture at the Académie Julian in Paris with Mercié and Emmanuel Frémiet. He became an accomplished 'animalier' (animal sculptor). He exhibited several pieces at the Salon including small groups of rabbits, a bust of a black man, a sketch from an American Indian group, and a sleeping faun with a rabbit. For the 1893 World Columbian Exposition in Chicago, Potter collaborated with his teacher and friend Daniel Chester French, on the sculptures for the exposition. The statues were made of a mixed-media material, called 'staff,' which was made from a mixture of plaster, cement, and jute fibers. It was first used for buildings and large monuments at the Paris exhibition in 1878. Since the exhibitions were generally broken down after the fairs, much of what Potter and others had created was destroyed.

In 1893, Potter was admitted to the National Sculpture Society. In 1894, he joined the Society of American Artists, which later merged with the National Academy of Design. He settled in Greenwich, CT, in 1902, when he sculpted a monument to Colonel Raynal Bolling, the first high-ranking officer to be killed in WWI. Potter won the gold medal for sculpture at the St. Louis Exposition in 1904. He was a founder and the first president of the Greenwich Society of Artists (1912).

Potter is most remembered for his two large, Tennessee marble, lions flanking the exterior steps of the New York Public Library main building (designed by Carrere and Hastings). They were carved in 1911 in the workshops of the Piccirilli brothers. Mayor Fiorello LaGuardia nicknamed the lions 'Patience' and 'Fortitude,' and they are among the best-known public statues in New York City.

He began his career representing the striking workers after the Triangle Shirtwaist Factory fire (1911). LaGuardia ran for Congress on the Republican ticket in 1914. He was defeated, but mounted a campaign against the Tammany machine in 1916, which he won.

WWI interrupted his political career. In 1917, he commanded the U.S. Air Force on the Italian-Austrian front. Between 1920 and 1933-1933, his activities focused on New York City and Congressional politics. He fought for healthcare and housing for the poor, and the regulation of food standards. To make his point on the latter issue, he would wave slabs of raw meat in the House of Representatives while giving impassioned speeches.

LaGuardia was elected mayor of New York City in 1933 and he pursued reform by fighting political corruption. His other priorities were slum clearance, the improvement of health and sanitary conditions, and the general beautification of the city. He was responsible for New York's first airport, which still bears his name. His good works earned him national recognition and a fond nickname, the translation of his Italian first name: 'Little Flower.' On the downside, he earned a reputation for wildly expanding city government, and as an extravagant spendthrift of taxpayer money.

The Piccirillis' workshop garnered them commissions to carve other artists' designs. They carved marble sculptures designed by John Quincy Adams Ward, Augustus Saint-Gaudens, and R.I. Aitken. The Piccirilli studio won the commission for the monument to the Battleship Maine (at the southwest corner of Central Park, dedicated in 1913). This was followed by a more important commission — to carve the statue of Lincoln designed by Daniel Chester French for the Lincoln Memorial in Washington, DC (dedicated 1922). Attilio designed the World War I monument in Albany, NY, and made it in their workshop. In 1931, Attilio carved a bust of Thomas Jefferson for the state capitol in Richmond, VA. He modeled the bust after an earlier version by Jean-Antoine Houdon.

The family continued to create the exterior sculptures for New York landmarks: the Brooklyn Museum of Art, the New York Stock Exchange; the pediment sculptures for the U. S. Customs House at Battery Park; the lions in front of the New York Public Library; City Hall Park; and a frieze for the Life Building at Rockefeller Center.

The brothers, and particularly Attilio, were respected members of the Italian-American community; Attilio dined with Enrico Caruso, the famous opera tenor, at the home of Fiorello LaGuardia. He was president of the Italian-American Art Association, a fellow of the National Academy of Design, and founded the Leonardo da Vinci Art School, to which he devoted great energy over the years. By the 1930s, the number of sculpture commissions dwindled, in part due to the Depression, but also because of changing taste. Public sculpture simply fell out of favor.

The 'family seat' in the USA was their home and workshop at 467 E. 142nd St. As was the practice at the time, the extended family lived together at this location. Attilio and his brother Getulio died within three days of each other in 1945. The Piccirilli studio was demolished sometime in the 1960s, and the documents and possessions of the family have disappeared.