Frank W. Eldredge was born in Broome County, New York in March 1849, the son of Hobart and Charlotte (Tompkins) Eldredge. The family was living in the Town of Chenango at the time of the 1850 census, with Hobart's occupation given as "Lumber Manufacturer." In the 1860 census they are living in Ward 1, Binghamton. Frank's younger sisters Helen and Caroline are listed, but the childrens' ages are all increased by ten years (Frank is listed as 21, instead of 11). Hobart Eldredge died in California later in 1860; Frank's diary entries mentions that his sisters are in California. Frank's mother Charlotte later remarried, taking as her second husband James Eldredge, Hobart's older brother.

Frank Eldredge attended the Eagleswood Military Academy from 1862 to 1865. In the 1870 census he is living in Chester, Morris County, New Jersey, working as a railroad employee (his age in 1870 is given as 22). On June 29, 1882 he married Estelle Hollenbeak or Hollenbeck in Indiana; the couple had six children. By 1900 the family was living in De Kalb, Kershaw County, South Carolina, where Frank's occupation is given as "Hotel Proprietor," and in 1910 they are recorded at Camden, Kershaw County. Frank Eldredge died there in May 1912. There is a large grave marker in the Quaker Cemetery, Camden, South Carolina memorializing this family, including Frank's mother and stepfather and his sisters. A short obituary for Frank W. Eldredge appeared in the May 20, 1912 issue of the Binghamton Press and Leader, noting that "Numerous Binghamtonians have stayed at the Hopkirk Inn in Camden, [South Carolina] of which Mr. Eldredge was proprietor."

The diary mentions several of his Tompkins relatives, including "Uncle Phin," his mother's brother Phineas Tompkins, and cousins Helen and Nellie (Ellen), Phineas' children.