| Political Party | Democratic |
| Term | December 9, 1875 - January 8, 1880 (48-53) |
| Lieutenant Governor | James A. Johnson |
| Predecessor | Romualdo Pacheco |
| Successor | George C. Perkins |
| Full Name | William Irwin |
| Birth |
January 1, 1827 Butler County, Ohio |
| Father | David Irwin (1802-1842) |
| Mother | Nancy Moore (1805-1879) |
| Brothers |
James Irwin (1832-1860) David Irwin Jr. (1841-1911) |
| Sisters | Britten Irwin (1830-1830) |
| Alma Mater | Marietta College (1848) |
| Occupation |
Member of the Board of Harbor Commissioners of California (1880-1886) 10th Lieutenant Governor of California (1875) California State Senator (1869-1875) Town Trustee of Yreka, California (1865-1866) Member of the California State Assembly (1863-1865) Educator |
| Death |
March 15, 1886 San Francisco, California (59 years) |
| Amelia Elizabeth Cassidy (1843-1905) |
Married December 21, 1865 (20 years) |
| Emma Vasty Irwin |
Born 1866 Died 1943 (77 years) |