Benjamin Mayfield, the second son of American pioneer farmer William Mayfield and his first wife, was born in Illinois in 1831. His father moved the family to Texas in 1837, where he and his older brother John grew up in Washington County and his brother Thomas Jefferson Mayfield was born in 1843. There his mother died sometime before his father was married to his second wife Mary Ann Curd on March 16, 1848.
When Benjamin was 18, in 1849 his father moved the family again to California, with a U. S. Army wagon train but were sent back to avoid the danger to civilians from the Lipan Apache on the trail and they then took a six-month trip by ship from Galveston around Cape Horn to reach California. After they landed at San Francisco, William took his family to the southern end of the San Joaquin Valley, then Mariposa County, now Tulare County to a place at the confluence of Sycamore Creek with the Kings River, (about 1.5 miles above modern Trimmer, California). There Ben and his older brother John helped his father build a cabin, put in crops and began mining. 
Mary Mayfield died in December 1850, and in 1851, William Mayfield left eight-year-old Thomas to be raised by the Choinumni, the friendly Yokut tribe living across the river from his cabin, while he and his two older sons left to engage in mining and raising cattle for the next 10 years. With his father and brother Benjamin ran cattle and horses through most of the San Joaquin Valley, captured wild horses on the west side of that valley and fought Monache on the east side, his father becoming well known throughout the valley.
William Mayfield died on April 9, 1862, leading Tulare County militia in the Battle of Mayfield Canyon early in the Owens Valley Indian War. After his death Benjamin went to Southern California and became a miner in the Lytle Creek mines.
Killing of John Mason and the Trials of Benjamin Mayfield
In April 1866, the outlaw John Mason intercepted and joined Benjamin Mayfield on the ride to Fort Tejon from his mine in Lytle Creek. Benjamin knew of him and that there was a $500 reward on Mason's head. However Mason was also protected by the large number of pro secessionists in that part of the state, that made collecting the bounty dangerous. Mason later tried to recruit him into his gang. When Ben refused, Mason threatened to kill him. Mason had also threatened to take the horse of another man W. H. Overton and kill him. That night while the three were in the same house, none went to sleep but in the early morning Mason lay down on his bed under a blanket, but was awake. Overton stepped out to look after his horse, then Mason tried to shoot Mayfield from his bed. Mason's pistol tangled in his blanket, giving Mayfield the chance to shoot him first. Fearing reprisal from the gang or his secessionist friends, Mayfield and Overton carried Mason out on his bed and buried them in an unmarked grave, but his body was later found.
Mason's death was announced in the Stockton Daily Independent, SATURDAY, April 21, 1866:
- MASON, the DESPARADO, KILLED – Visalia, April 20 – MASON, of the distinguished firm of MASON & HENRY, was killed a few days since in Tejon cannon[canyon], by some citizens. There appears to be but little doubt that this is the veritable MASON. It seems there were several of his clan together and they all got off except the chief.
Mayfield and Overton for their pains were not rewarded but were accused of murder by friends of Mason, and tried for murder in Los Angeles County.
The Sacramento Daily Union, June 23, 1866, quotes the The Wilmington Journal on the verdict:
- On the evening of June 8, the jury in the case of Benjamin Ben Mayfeild, who murdered the highwayman John Mason, returned a verdict of guilty of murder in the first degree. The next day he was sentenced to be hung on August 1. The counsel of the murderer Intend to carry the case to a higher Court if possible.
Mayfield's appeal resulted in a second trial in September 15, 1866. The jury again found the defendant guilty of murder in the first degree and the counsel for the defense asked for a new trial, which was refused by Judge de la Guerra. The prisoner was sentenced to be hanged in August 1867. On application to the Supreme Court a stay of proceedings was granted.
Exonerated in 1869, Benjamin died an embittered man sometime in the 1870s.
- 1850 Census, Mariposa County, CA, p. 47 Nov. 13, 1850
- Thomas J. Mayfield, Indian summer: traditional life among the Choinumne Indians of California's San Joaquin Valley, Heyday Books, Berkley, 1993, p.25
- Brazos County Early Marriages: William Mayfield to Mary Ann Curd, 16 Mar 1848
- Mayfield, Indian summer, pp.26–27
- Mayfield, Indian summer, pp.26–42
- The November 13, 1850 census, shows Mayfield 40 with $10,000 in property and his son John 20 as miners. His son Ben 16 (should be 18) is listed separately with Mary 20 and her child S [or T] Willson Mayfield 7, presumably at the cabin. 1850 Census, Mariposa County, CA, p. 49 Nov. 13, 1850
- [Mayfield, Indian summer, p.22]
- Daily Alta California, Volume 18, Number 6032, 16 September 1866 — LOS ANGELES NEWS. THE CASE OF MAYFIELD IN LOS ANGELES. The Testimony of Mayfield in Relation to the Killing of Mason.
- Newspaper Abstracts, Stockton Daily Independent, SATURDAY, 21 APR 1866
- Sacramento Daily Union, Volume 31, Number 4755, 23 June 1866 — NEWS OF THE MORNING.
- Daily Alta California, Volume 18, Number 6032, September 16, 1866 – LOS ANGELES NEWS. THE CASE OF MAYFIELD IN LOS ANGELES.