Parsons was born in Washington DC, and raised to practice law in his fathers law firm. However, he became disillusioned with that field of work, and for a time he worked as a salvager in Florida, salvaging shipwrecks, beginning around 1874. After a near death experience while working in Cape Sable, during a hurricane, Parsons decided to find another line of work, and moved to California, where he worked as a bank clerk for three years in Los Angeles, starting in 1876. He then began working for the National Gold Bank & Trust Co., but when the bank closed down in 1880 he found himself out of work, and moved with Milton Clapp to the boomtown of Tombstone, Arizona, where he became associated with John Clum, who was mayor as well as editor of the Tombstone Epitaph.
He had began writing his diaries in 1869, following the death of his mother, an event he would make note of on its anniversary every year afterward. However, it was the events he was witness to in Tombstone which made the diaries a desired read. He became a member of the "Committee of Vigilance" in Tombstone, an organization of local citizens in support of law and order, which brought him into regular contact with lawmen Fred White, Wyatt Earp, Virgil Earp, Johnny Behan, and Morgan Earp. He also knew Ike Clanton, "Curly Bill" Brocius, Johnny Ringo and others of note. For the next seven years Parsons would keep daily records of his day, and detailed what happened leading up to, during, and after the Gunfight at the OK Corral. The diary would later give valuable insight into the personalities of the characters involved in those events, all of which have since become famous or infamous. He also documented and described other events of note, to include the grand opening of the Oriental Saloon, which would become famous in Old West history.
Parsons was, in 1885, the first librarian for the Tombstone Library, and in 1887 he left Tombstone, which by that time was on the decline. Parsons stopped writing in his diary in 1929. Editor Carl Chafin later spent several years researching the diary, and later published the portions covering 1879 to 1887. Parts of the diary was donated to the Arizona Pioneers Historical Society during the 1930s, after Parsons death. Parsons died in Los Angeles, and was buried in "Evergreen Cemetery". His diaries can still be found, most notably in the book "A Tenderfoot in Tombstone, the Private Journal of George Whitwell Parsons: The Turbulent Years, 1880-82", authored by Lynn R. Bailey.