Rockwell's family moved to New Rochelle, New York, when Norman was 21 years old. They shared a studio with the cartoonist Clyde Forsythe, who worked for The Saturday Evening Post. With Forsythe's help, Rockwell submitted his first successful cover painting to the Post in 1916, Mother's Day Off (published on May 20). He followed that success with Circus Barker and Strongman (published on June 3), Gramps at the Plate (August 5), Redhead Loves Hatty Perkins (September 16), People in a Theatre Balcony (October 14), and Man Playing Santa (December 9). Rockwell was published eight times on the Post cover within the first year. Ultimately, Rockwell published 323 original covers for The Saturday Evening Post over 47 years. His Sharp Harmony appeared on the cover of the issue dated September 26, 1936; it depicts a barber and three clients, enjoying an a cappella song. The image was adopted by SPEBSQSA in its promotion of the art.
When Rockwell's tenure began with The Saturday Evening Post in 1916, he left his salaried position at Boys' Life, but continued to include scouts in Post cover images and the monthly magazine of the American Red Cross. He resumed work with the Boy Scouts of America in 1926 with production of his first of fifty-one original illustrations for the official Boy Scouts of America annual calendar, which still may be seen in the Norman Rockwell Art Gallery at the National Scouting Museum in the city of Cimarron in New Mexico.
Rockwell married his first wife, Irene O'Connor, in 1916. Irene was Rockwell's model in Mother Tucking Children into Bed, published on the cover of The Literary Digest on January 19, 1921. The couple divorced in 1930.