Helen Moore Sewell was born into an affluent family, in Mare Island Navy Yard, Vallejo, California in 1896. Her father’s later appointment as Governor to the island of Guam introduced a life of travel to the young Helen, and her work would be influenced by this travel throughout her life.

The family moved to New YorkShe where, at age 12, she became the youngest pupil to attend the Pratt Institute, for Saturday classes. She formally enrolled at age 16. She would study under Charles Hawthorne and later with Alexander Archipenko, who remained a great influence to her. In 1924 she illustrated her first children’s book, and by 1931 had begun writing and illustrating her own.

Some of her first serious sales were to the Christmas and greeting card markets, and in 1924 she became a published children's book illustrator with The Cruise of the Little Dipper and Other Fairy Stories. She was also the original illustrator for the Little House books, some co-illustrated with Mildred Boyle.

Children were always an important part of Sewell's life. "It was natural that I should turn to making pictures for children," she once said. "Good art for children must be intelligible to them, so I have always gone to children for my cue and inspiration, and I have found them a rewarding and appreciative public." Ms. Sewell died in 1957.