Appointed: March 1874 - April 1874
Leroy Dennis was born at Fort Osage Township, Jackson County, Missouri in 1842. Dennis' presence in California is first noted in the Federal Census of 1860; he resided in Visalia, Tulare County, as an eighteen-year-old laborer.
In 1870, Dennis was a saloonkeeper who was married and had two daughters and one son residing with him at Buchanan Hollow, Fresno County.
He was appointed Road Master of District #7 by the Board of Supervisors. Dennis announced his candidacy for the office of Sheriff in the April 9, 1873 Fresno Expositor.
Leroy Dennis was elected Sheriff–Tax Collector of Fresno County on September 3, 1873; 762 were votes cast countywide and Dennis defeated the incumbent J. Scott Ashman by twelve votes. Sheriff Dennis was installed and assumed the duties of his office on March 2, 1874. Dennis appointed two Deputies, A. Witthouse and William Rousseau as Undersheriffs. The jail and the lack of security provided for inmates and jailers, was a regular topic in the press. On March 3, 1874, a Tuesday, Sheriff Dennis' courage was put to the test. Dennis was called by one of two inmates housed in the jail. Inmate Ignacio Rangel, a member of the Vasquez gang who was captured at Rancho California, informed the Sheriff that inmate Grace had a gun, and had threatened to kill him. Dennis went into the jail and discovered that Rangel had managed to get Grace into a cell and close the door. Grace told Dennis that he was in his own house (cell) and that if Dennis tried to enter he would be shot. Dennis wisely told Grace that he was welcome to stay and locked down the jail. Dennis returned the next morning and went into Grace's cell. Grace gave Dennis his Colt's cartridge derringer. Dennis determined that someone passed the pistol to Grace through the bars from the outside. The Fresno Expositor opined anything could and often was passed from the outside to inmates within the jail, with bottles of whiskey being the most common item. The paper said the jail was too dangerous for officers who had to work within its confines and suggested a new jail and courthouse be built in a new County Seat where officers would not take their lives in their own hands every time they entered the jail.
Sheriff Dennis died while in office on Saturday, April 25, 1874. Coroner Heaton assumed the duties and responsibilities of the office of Sheriff until J. Scott Ashman was appointed by the Board of Supervisors.