William was born with middle name of Lewis, he changed it. William was a captain in the LA police Dept, veteran of Spanish American War. He was compiling Hagenbuch history in the 1920s until his death in 1943. He had much research but it was destroyed by a fire after his death. Death date from Findagrave.
| 21 Mar 1878 – | William L. Hagenbaugh born |
| 26 Apr 1903 – | Married Ida M. (James) Hagenbaugh |
| 28 May 1904 – | Son William R. Hagenbaugh born |
| 1912 – | Divorced Ida M. (James) Hagenbaugh |
| 11 Nov 1912 – | Married Lillian L. (Norquist) Hagenbaugh |
| 9 Sep 1913 – | Daughter Dorothy L. (Hagenbaugh) Abreu born |
| 9 Sep 1918 – | Daughter Mildred L. (Hagenbaugh) McDade born |
| 20 May 1921 – | Son Robert L. Hagenbaugh born |
| 19 Feb 1943 – | William L. Hagenbaugh died in Los Angeles, Los Angeles County, California, United States |
| 20 Feb 1943 – | William L. Hagenbaugh buried |