| TERM | NAME |
| May, 1889 through April, 1891 | John McBride |
| May, 1891 through April, 1893 | O.F. Biglin |
| May, 1893 through April, 1895 | R.R. Dickson |
| May, 1895 through April, 1896 | O.F. Biglin |
| May, 1896 through April 1897 | H.E. Murphy |
| May, 1897 through April 1898 | B.S. Gillespie |
| May, 1898 through April, 1899 | C.L. Davis |
| May, 1899 through April, 1900 | John A. Harmon |
| May, 1900 through April, 1903 | Ed F. Gallagher |
| May, 1903 through April, 1905 | J.S. Harrington |
| May, 1905 through April, 1906 | D.A. Doyle |
| May, 1906 through April, 1909 | Ed F. Gallagher |
| May, 1909 through April, 1914 | O.F. Biglin |
| May, 1914 through April, 1915 | T.V. Golden |
| May, 1915 through April, 1917 | F.J. Dishner |
| May , 1917 through October, 1918 | Edward H. Whelan |
| Nov., 1918 through April, 1919 | P.D. Mullen |
| May, 1919 through April, 1920 | Clyde King |
| May, 1920 through April, 1922 | C.M. Daly |
| May, 1922 through April, 1926 | J.P. Gilligan |
| May, 1926 through April, 1934 | C.E. Stout |
| May, 1934 through April, 1938 | John Kersenbrock |
| May, 1938 through April, 1940 | H.E. Coyne |
| May, 1940 through April, 1946 | John Kersenbrock |
| May, 1946 through April, 1948 | F.J. Dishner |
| May, 1948 through April, 1950 | H.E. Coyne |
| May, 1950 through May, 1954 | J.E. Davis (Resigned) |
| June, 1954 through April, 1955 | Emmet Crabb (Acting Mayor) |
| May, 1955 through April 1956 | A. Marcellus |
| May, 1956 through April, 1964 | D.C. Schaffer |
| May, 1964 through April, 1965 | E. M. Gleeson (Acting Mayor) |
| May, 1965 through April 1968 | E.M. Gleeson |
| May, 1968 through 1974 | John J. Harrington |
| 1974 - 1978 | Randall Fitch |
| 1978 - 1984 | E.M. Gleeson |
| 1984 - 1984 | Wm. S. Mattern (Acting Mayor) |
| 1984 - 1990 | Lois Schaffer |
| 1990 - 1994 | Dennis Shannahan |
| 1994 - 1995 | Art Tibbetts |
| 1995 - 1996 | Betty Boyle (Acting Mayor) |
| 1996 - 1998 | Jack Hollenbeck |
| 1998 - 1998 | Wm. Price (Acting Mayor) |
1998 - 2018 | Wm. Price |
| 2018-Present | Scott Menish |
O'Neill, county seat of Holt County, was founded by General John O'Neill, a native of Ireland and veteran of the American Civil War. The "general," a rank bestowed on him by admirers because he commanded three Fenian incursions into British-governed Canada, first directed colonists in 1874 to this fertile Elkhorn Valley site which bears his name. General O'Neill also induced other Irish groups to settle at Atkinson in Holt County and in Greeley County.
Many Irish coming to O'Neill had emigrated to America earlier, as result of famine and economic distress, temporarily settling in eastern cities. General O'Neill, knowing the agricultural heritage of his people, said his object in founding Nebraska colonies was "to encourage poor people in getting away from the overcrowded cities of the East."
The Irish were a major immigrant group contributing to the settlement of Nebraska. Speaking the English language, they blended into the population and were found in many communities. However, due to ancient animosities with Britain, some of them colonized in America. Foremost colony in this state is O'Neill, proclaimed the Irish Capital of Nebraska by the Governor in 1969.
History of O'Neill, Nebraska
"Nebraska's Irish Capital"
City of O'Neill