O'Neill arrived in Prescott in the spring of 1882.
There he rapidly progressed in his journalistic career.
Starting as a court reporter, he soon founded his own newspaper, Hoof and Horn, a paper for the livestock industry.
He became the editor of the Arizona Miner weekly newspaper in 1884 to February 1885.

He became captain of the Prescott Grays in 1886, the local unit of the Arizona Militia.
On February 5, 1886, Dennis Dilda, a convicted murderer, was hanged.
O'Neill and the Prescott Grays stood honor guard for the event.
When the trap dropped, O'Neill fainted, which caused him severe embarrassment.
He later wrote a story called "The Horse of the Hash-Knife Brand."
In it, a member of a posse admits to nearly fainting at the hanging of a horse thief.

On April 27, 1886, he married Pauline Schindler.
They had a son, but he died shortly after being born premature.

In 1888, while serving as Yavapai County, Arizona judge, he was elected county sheriff, running on the Republican ticket.

On March 20, 1889, four masked men robbed the Atlantic and Pacific Railroad passenger train in Diablo Canyon.
A four-man posse, made up of O'Neill, Jim Black, Carl Holton, and Ed St. Clair, was soon formed and they took off after robbers.
On March 21, O'Neill and his posse caught up with the robbers.
After exchanging rifle shots, the posse captured the four men.
During the fight, no men were injured, but O'Neill's horse was killed.

The four men were William Sterin, John Halford, Daniel Harvick, and J. J. Smith.
All four were sent to the Yuma Territorial Prison, but were pardoned eight years later.
There is unfounded speculation that, in 1898, William Sterin enlisted under a false name in the Rough Riders, and was killed in action on San Juan Hill.
The character of Henry Nash is incorrectly portrayed as Sterin in the TNT made-for-TV movie "Rough Riders".
The real Henry Nash was an Arizona school teacher who also served in Roosevelt's Rough Riders, and was a friend of O'Neill up until his death.

After his term was up, O'Neill was elected unanimously mayor of Prescott.

In 1894 and 1896 he ran for Delegate to the United States House of Representatives from Arizona Territory, running on the Populist Party ticket.

One of his best friends was Tom Horn.

In 1897, after years of speculating on mines, he sold a group of claims near the Grand Canyon to Chicago backers, who also proposed building a railroad from Williams to the mines and the south rim.
 He became a director of the development companies, and soon began railroad surveys, mine developments, and building a smelter.
 He also used profits to begin building rental buildings—he was headed for financial independence.

O'Neill also helped introduce a bill allowing women to vote in municipal elections in 1897.
Although O'Neill convinced his Populist friends to sign the bill into law, the high court dismissed the bill in 1899.
O'Neill arrived in Prescott in the spring of 1882. There he rapidly progressed in his journalistic career. Starting as a court reporter, he soon founded his own newspaper, Hoof and Horn, a paper for the livestock industry. He became the editor of the Arizona Miner weekly newspaper in 1884 to February 1885.
He became captain of the Prescott Grays in 1886, the local unit of the Arizona Militia. On February 5, 1886, Dennis Dilda, a convicted murderer, was hanged. O'Neill and the Prescott Grays stood honor guard for the event. When the trap dropped, O'Neill fainted, which caused him severe embarrassment. He later wrote a story called "The Horse of the Hash-Knife Brand." In it, a member of a posse admits to nearly fainting at the hanging of a horse thief.
On April 27, 1886, he married Pauline Schindler. They had a son, but he died shortly after being born premature.
In 1888, while serving as Yavapai County, Arizona judge, he was elected county sheriff, running on the Republican ticket.
On March 20, 1889, four masked men robbed the Atlantic and Pacific Railroad passenger train in Diablo Canyon. A four-man posse, made up of O'Neill, Jim Black, Carl Holton, and Ed St. Clair, was soon formed and they took off after robbers. On March 21, O'Neill and his posse caught up with the robbers. After exchanging rifle shots, the posse captured the four men. During the fight, no men were injured, but O'Neill's horse was killed.
The four men were William Sterin, John Halford, Daniel Harvick, and J. J. Smith. All four were sent to the Yuma Territorial Prison, but were pardoned eight years later. There is unfounded speculation that, in 1898, William Sterin enlisted under a false name in the Rough Riders, and was killed in action on San Juan Hill. The character of Henry Nash is incorrectly portrayed as Sterin in the TNT made-for-TV movie "Rough Riders". The real Henry Nash was an Arizona school teacher who also served in Roosevelt's Rough Riders, and was a friend of O'Neill up until his death.
After his term was up, O'Neill was elected unanimously mayor of Prescott.
In 1894 and 1896 he ran for Delegate to the United States House of Representatives from Arizona Territory, running on the Populist Party ticket.
One of his best friends was Tom Horn.
In 1897, after years of speculating on mines, he sold a group of claims near the Grand Canyon to Chicago backers, who also proposed building a railroad from Williams to the mines and the south rim.  He became a director of the development companies, and soon began railroad surveys, mine developments, and building a smelter.  He also used profits to begin building rental buildings—he was headed for financial independence.
O'Neill also helped introduce a bill allowing women to vote in municipal elections in 1897. Although O'Neill convinced his Populist friends to sign the bill into law, the high court dismissed the bill in 1899.
Buckey O'Neill