Franklin Benjamin Sanborn was born at Hampton Falls, New Hampshire, on December 15, 1831. His parents were Aaron Sanborn and Lydia Leavitt. Sanborn was the second eldest child with siblings Dr. Charles Henry Sanborn (born 1821), Lewis Thomas Sanborn (born 1834), Sarah Elizabeth Sanborn (born 1823), and Helen Maria Sanborn (born 1830). A younger brother, Joseph Leavitt Sanborn died in infancy in 1872.
Sanborn was educated at the Phillips Exeter Academy in New Hampshire and at Harvard College (1852-55). While at Exeter, he also studied Greek privately with J.G. Hoyt, who is mentioned frequently in letters by Sanborn's friends from Exeter days. As a student Sanborn became deeply influenced by Transcendentalist writer Ralph Waldo Emerson and the abolitionist and reformer Rev. Theodore Parker.
In July 1853, a ten-minute visit to Emerson initiated a lifelong friendship. In March 1855, Emerson invited Sanborn and his sister Sarah to take charge of a small private school begun by John and Henry Thoreau, which was attended by Emerson's own children among others. Subsequently, on Emerson's recommendation, Sanborn moved into the home of the poet William Ellery Channing then living near the school in Corcord, Massachusetts. The latter was closely acquainted with other local authors who, along with Emerson, included Nathaniel Hawthorne and Henry David Thoreau, with whom Channing was in the habit of rambling through the countryside made famous in their writings. Thus began, for Sanborn, a lifetime's association with Concord's famous inhabitants. Other notable individuals he would come to know there included Amos Bronson Alcott, Louisa May Alcott, Margaret Fuller, Charles Lane, and Rev. Theodore Parker.
One of the more controversial figures that Sanborn met through Channing was the abolitionist John Brown. Through both associations Sanborn soon became deeply involved with the movement. He was a member of the Free-Soil Party in New Hampshire and Massachusetts, and in 1856, became secretary and active member of the Massachusetts State Kansas Committee, raising funds for the Free State cause. At one point in the summer of 1856, he drove across the states of Indiana, Illinois and Iowa, as well as the Territory of Nebraska on a fundraising tour for the Committee.
Sanborn first met Brown in late 1856, when the latter was given a letter of introduction by George Walker, brother of Sanborn's wife, Ariana. Sanborn became a zealous disciple and was a member of Brown's "Secret Six" who were the only men to know in advance of the Harper's Ferry raid. After the raid, Sanborn fled to Canada, but returned at Emerson's request under an assumed name. On April 3, 1860, deputies of the U.S. Senate attempted to kidnap Sanborn, but a crowd of Concord citizens, including Emerson prevented the arrest. Charges against Sanborn for refusing to testify against Brown were eventually dropped based on a writ of habeas corpus.
In the 1860s, when the Civil War compelled him to close down the school in Concord, Sanborn turned increasingly to writing and newspaper work. He was Boston correspondent for the Springfield "Republican," in 1856, later becoming resident editor (1868-1906). Sanborn was also editor for the Boston "Commonwealth" (1863-67), and of the "Journal of Social Science" (1876-97).
After Harper's Ferry, a continuing interest in social reform led to Sanborn's aiding in the establishment of the American Association for the Promotion of Social Science and his forming the first college course in social science at Cornell University where he was special lecturer from 1884 to 1887. Prior to that, on the recommendation of George Walker, he gained an appointment on the newly created Board of State Charities, in 1863. With Amos Bronson Alcott and William Torrey Harris, Sanborn also co-founded the Concord School of Philosophy (1878-88), a summer school that featured lectures by Alcott, Emerson, Frederic Henry Hedge, and Sanborn, himself.
In later years, Sanborn cultivated his Concord connections, producing numerous biographical works on A. Bronson Alcott, Emerson, Hawthorne, Thoreau, as well as editing works by William Ellery Channing and Rev. Theodore Parker. In 1860, Sanborn was named one of Parker's executors although the will left the disposition of papers in the hands of Parker's wife, Lydia Dodge Cabot, until her death when she ultimately bequeathed them to Sanborn. In 1891, Sanborn persuaded William Ellery Channing to move into his house, the latter proving an invaluable source for his biographical work on Emerson and Thoreau.
In 1853 Sanborn was engaged to Ariana Smith Walker whom he married shortly before her death from a long illness in the summer of 1854. Sanborn died on February 24, 1917, five weeks after being struck by a baggage wagon on a train platform in Plainfield, New Jersey.
Sanborn's principal works include: "Henry David Thoreau" (1882); "Life and Letters of John Brown" (1885 with later editions); "A. Bronson Alcott: His Life and Philosophy," 2 vols. (1893); "Ralph Waldo Emerson" (1901); and an autobiography, "Recollections of Seventy Years," 2 vols. (1909). Sources: "Dictionary of Literary Biography," Vol. 1 (Detroit: Gale Research Co., 1978); and "Recollections of Seventy Years," 2 vols., by Franklin B. Sanborn (Boston: Gorham Press, 1909).