Monihon was born to James and Ann (Martin) Monaghan, Irish immigrants, in
Oneida County, New York on November 6, 1837. When he was two, his family moved to
St. Lawrence County where he grew up on a farm and attended local schools. Monihon joined the
California Gold Rush in 1854, traveling by sea via the
Isthmus of Panama. After reaching
San Francisco, California, he became involved in
placer mining often around
Howland Flat,
Sierra County until 1861. At the beginning of the
Civil War, Monihon enlisted in Company F of the
1st California Infantry Regiment. While in the military, he served throughout the area that composes modern day
Arizona and
New Mexico. As Chief of the Howitzer division he fired a celebratory salute in
Tucson on July 4, 1862. Ten days later he saw action during the
Battle of Apache Pass when his unit of 64 soldiers was attacked by over 450
Apache Indians led by chief
Cochise. Following the battle, his unit spent two months in
Mesilla before being redeployed to
Fort Craig. In late 1863, Monihon's unit was ordered to
Fort Wingate. From there they continued to the
Chino valley where they established
Fort Whipple. Monihon served as
Provost Sergeant at his new posting until his
discharge at the end of the war. He remained in central Arizona, where he worked in mining again for several years and ran a
livery stable in Prescott. Much of his mining work was as engineer of the mill at the
Big Bug mine. In 1868, Monihon sold the livery business, the Plaza Feed and Livery Stable, to
Gideon Brooke and Jacob Linn.
George M. Willing tried to sell him half ownership in the fraudulent
Peralta land grant for $250 (~$ in ) in 1867. Willing suggested that the two of them could reap a sizable profit by selling nearby mines back to their owners. Monihon was incensed by the offer and rebuffed Willing who quickly left town. Almost 30 years later, Monihon testified as a principal witness for the government about this in court after the fraud was exposed. Monihon relocated to
Wickenburg and in March 1869, opened the Wickenburg Feed and Sale Stable. ==Phoenix==