Kate Douglas Smith Wiggin, the daughter of Helen E. Dyer and Robert Noah Smith, was born on September 28, 1856, in Philadelphia. Robert Smith died when Kate was three years old, and Helen Dyer Smith took her two daughters to Portland, Maine. Kate's mother married Dr. Albion Bradbury in 1863, and the family moved to the nearby town of Hollis, Maine, where they lived until 1873, when they moved to Santa Barbara, California. Wiggin finished her studies at Abbott Academy in Andover, Massachusetts, before joining her family several months later.
During her childhood, Wiggin enjoyed a chance encounter with Charles Dickens on a train trip between Portland and Boston. She described this meeting in A Child's Journey with Dickens and again in her autobiography, My Garden of Memory. Her schooldays at Gorham Female Seminary inspired her first published story, "Half a Dozen Housekeepers," accepted by St. Nicholas magazine in 1876.
In 1877 Wiggin became acquainted with the German educator Friedrich Froebel's concept of the kindergarten, and the next year she established the Silver Street Kindergarten in San Francisco, the first free kindergarten west of the Rocky Mountains. In 1880 she opened a training school for kindergarten teachers, including her younger sister Nora A. Smith, with whom she later wrote several books on educational theories and techniques. Wiggin's first two books, The Birds' Christmas Carol and The Story of Patsy, were privately published to raise money for the kindergarten project.
Wiggin continued her kindergarten work after she married Samuel Bradley Wiggin in 1881. Although they moved to New York in 1884, she returned to California each spring to supervise the kindergarten. In 1889, while Wiggin was in California, her husband died suddenly. Wiggin continued to live in New York until 1893, when she moved with her mother and her sister to Hollis, Maine.
After her husband's death, Wiggin made almost annual ocean voyages to Europe, and on one such voyage she met George C. Riggs, a New York businessman whom she married in 1895. Riggs's business interests required frequent trips to England, Scotland, Ireland, and Germany, and Wiggin traveled widely with him. She died on August 24, 1923, at Harrow-on-the-Hill, England.