Newell Hillis Arnold was born in Rural Beach, North Dakota on 10 Jun 1906 to Meda and Algie Arnold. At six months old, he contracted meningitis, which left him deaf. Arnold's mother took notice of her son's exceptional artistic abilities and encouraged his artistic development by giving him molding clay. In 1918, the family moved permanently to Minneapolis, where Arnold attended Minneapolis Day School for the Deaf for six years, then Minneapolis Central High School where he graduated with honors in 1928. In 1933, he graduated with honors from the University of Minnesota with a bachelor's degree in architecture. While at the university, he joined an honorary architectural fraternity and won the Keppel prize in sculpture. He then received a full scholarship to attend the Minneapolis School of Art (1933-1936).

During the summer of 1935, Arnold visited Cranbrook with his mother and met Carl Milles. After receiving a tuition scholarship, Arnold attended Cranbrook from 1936-1938, studying with Milles who commissioned him to assist him on several projects, including the Meeting of the Waters in St. Louis.

In 1938, on the recommendation of Milles, Arnold took a position as professor of sculpture and ceramics at Monticello College in Godfrey, Illinois, where he taught for the next thirty-four years. Arnold settled in Kirkwood, a St. Louis suburb, where he met and married Eulalia “Lee” Guebert in 1951. They had two daughters, Katherine and Caroline.

Arnold was renowned for his work in religious and symbolic subject matter – seventy-five percent of his work had a religious theme. He contributed sculptures to many churches and civic buildings in the Midwest. Arnold also exhibited widely throughout the United States and participated in national competitions such as the Roosevelt Memorial project in Washington, D.C. and the Jefferson National Memorial project, where he garnered honorable mentions. His work in St. Louis includes the World War II Memorial Court of Honor; Holy Cross Lutheran School for the Deaf; the St. Louis Abbey; and Resurrection Church. One of Arnold's biggest accomplishments was being selected, along with other artistic and literary greats such as Aldous Huxley and Thornton Wilder, as a Live Fellow of the International Institute of Arts and Letters.

In 1972, Arnold retired from Monticello and continued to work in his Kirkwood studio. He died at his home on 18 Nov 1988.