American author who led the kindergarten education movement in the United States.

Kate Douglas Smith attended a district school in Philadelphia and for short periods the Gorham Female Seminary in Maine, the Morison Academy in Maryland, and the Abbott Academy in Massachusetts. In 1873 she moved with her family to Santa Barbara, California. The death of her stepfather in 1877 left the family in perilous financial condition. At the suggestion of social reformer Caroline M. Severance (Severance, Caroline Maria Seymour), who also provided her room and board, Smith entered the Pacific Model Training School for Kindergartners headed by Emma Marwedel (Marwedel, Emma Jacobina Christiana).

For a time after completing the course, Smith directed a private kindergarten in Santa Barbara. In 1878 she headed the Silver Street Kindergarten in San Francisco—the first free kindergarten on the West Coast of the United States. In 1880, after further training under Susan Blow (Blow, Susan Elizabeth) and Elizabeth Peabody (Peabody, Elizabeth Palmer), Smith helped establish the California Kindergarten Training School. She remained head of the Silver Street Kindergarten until her marriage in 1881 to Samuel B. Wiggin, a lawyer. Despite her change in status, she continued to lecture at the training school, and even after her move to New York City in 1884 she returned to San Francisco each spring for the commencement exercises.

As a means of raising money for the training school, Kate Wiggin published privately The Story of Patsy (1883) and The Birds' Christmas Carol (1887). Commercial editions of both books issued in 1889 were great successes. After her husband's death in 1889, Wiggin retired for a time to Hollis, Maine, and there wrote Timothy's Quest (1890), a children's book. Thereafter she traveled frequently to Europe, especially after her marriage in 1895 to George C. Riggs, a New York businessman. Wiggin became a prolific writer of children's literature, travel books, and educational texts. Her subsequent books include Penelope's Progress (1898); Penelope's English Experiences (1900); Susanna and Sue (1909); Rebecca of Sunnybrook Farm (1910), probably her most popular work (dramatized by Wiggin in 1910 and first filmed in 1917); Penelope's Postscripts (1915); and Homespun Tales (1920).

With her sister, Nora A. Smith, Wiggin also wrote and edited a number of books, including The Story Hour (1890), The Republic of Childhood, 3 vol. (1895–96), on Froebelian (Froebel, Friedrich) kindergarten practice, and Kindergarten Principles and Practice (1896). In 1923, the year of her death, her autobiography, My Garden of Memory, was published.