Caleb Benjamin Tillinghast was born on April 3, 1843, in West Greenwich, Kent County, Rhode Island.

He was an editor and librarian. His family moved to Windham County, Connecticut, where he attended rural schools and worked on a farm. He held minor offices, both civic and in connection with the Good Templars. In 1870, he came to Boston, obtained a position as a reporter of the Boston Journal, and soon became city editor. In 1879, he was appointed Massachusetts State Librarian, remaining in this position until his death in 1909. For thirty years he served as clerk and treasurer of the State Board of Education, guiding the rapid development of education. When the Free Public Library Commission was created in 1890, he was appointed its chairman. He was a member of the Old Colony Historical Society, the Weymouth Historical Society, the Worcester Society of Antiquity, the Buffalo Historical Society, the Chicago Historical Society, the Western Reserve Historical Society, the American Antiquarian Society, the Boston Art Club, the Appalachian Mountain Club, the General Theological Library, the Massachusetts Total Abstinence Society, and the Boston Young Men’s Christian Union. Tillinghast received the honorary degree of M.A. from Harvard University in 1897, and the degree of Doctor of Literature from Tufts College in 1905.

In 1862, he married Ardelia M. Wood and in 1886, he remarried Martha M. Wonson (1834–1924). He died on April 28, 1909, in Boston, Massachusetts.