In 1863, he decided to settle in Arizona and first worked at a freighter at Fort Lowell, then at the Cerro Colorado Mine in Pima County, before moving on to the Prescott area, where he worked in various jobs. While prospecting along the Verde River, he and about five other men were attacked by Indians, but successfully fought them off on February 28, 1866.
That same year, he became the under sheriff of John P. Bourke in Yavapai County, Arizona where he gained a reputation as a brave and honest lawmen.
During this time, he also joined with civilian groups in investigating Indian attacks and married Victoria Zaff in1869. The couple would have two children.
By 1871, he was made the sheriff of Yavapai County, a position he held for two years. In 1873, he was the Prescott representative in the Seventh state assembly. In 1875, he and his wife divorced and Behan moved to Mohave County, where once again he was a state assembly representative, this time for Mohave County in 1879.
When mining in Tombstone began, he moved south and in 1880, became a deputy under Sheriff Charles A. Shibell of Pima County. When Cochise County, which included Tombstone, was organized in 1881, Behan became its first sheriff. Working for him as deputies were Frank Stilwell, William Breakenridge, Harry Woods, W.I. Perry, Bill Soule, H.L. Goodman and others.
Shortly after Behan became sheriff, Virgil Earp became the city marshal of Tombstone and recruited brothers Wyatt and Morgan as”special deputy policemen.” The Earps almost immediately came into conflict with the Clantons and the McLaurys, to whom Behan was an advocate. This naturally pitted him against the Earps. Adding further fuel to the fire, was Behan’s interest in Josephine Sarah Marcus, who was quickly becoming enamored with Wyatt Earp.
After the gunfight at the O.K. Corral on October 26, 1881, Behan arrested Virgil, Wyatt, and Morgan Earp, as well as Doc Holliday for the murder of Billy Clanton, Tom McLaury and Frank McLaury. However, the judge decided that the Earps and Holliday had been justified in their actions.
In September, 1882, after the Earp Vendetta Ride, Behan had a feud with his own deputy, William Breakenridge, which made him unpopular with Cochise County citizens. At the same time, investigations discovered that Behan had somehow banked some $5,000 during his tenure as sheriff. Where the money came from was never discovered.
In the end, public criticism of Behan resulted in his showing last on the ballot of possible sheriff nominees for his own party, an unusual result for a seated sheriff. Losing the nomination, he was forced out of office in November, 1882. He would never serve as a peace officer again.
In 1888, Behan became the Deputy Superintendent of the Territorial State Prison at Yuma, which prompted former Tombstone resident and writer George Parsons to suggest Behan was on the wrong side of the bars. Later, he served as a U.S. agent in El Paso, Texas, tasked with controlling area smuggling.
John Harrison Behan died of Brights Disease in Tucson on June 7, 1912 and was buried at a now-lost site in Tucson’s Holy Hope Cemetery.