In 1851 he moved from New York to California during the California Gold Rush.[1][2] He joined San Francisco's volunteer fire department, and enrolled in a local militia.
Scannell was San Francisco's third elected Sheriff, serving from 1855 to 1856.[1][2] When San Francisco Fire Department transitioned from an organization staffed by volunteers to one staffed by full-time paid staff Scannell served as its first fire chief.[1][2]
^ abcdef"David Scannell, San Francisco Sheriff 1855–1856". Guardians of the City. Retrieved 2014-10-13. He went on to become the Chief Engineer of the San Francisco Fire Department, and was appointed Chief in 1871 when the Fire Department went from a volunteer organization to a professional one. He died March 31, 1893 at the age of 73, much beloved by the citizens of the City.
^"THE CHIEF IS DEAD: David Scannell, Soldier, Fireman, Is at Rest". Vol. 73, no. 121. San Francisco Call. 1893-03-31. Retrieved 2014-10-13. For many months Chief Scannell's health bad failed rapidly, but with that indomitable iron will for which he was noted he struggled on with his dangerous duty in being the first at, all fires and the leader in their extinction.
^"The Chief is Dead". California Digital Newspaper Collection. The San Francisco Call, Volume 73, Number 121. 31 March 1893. Retrieved 2022-10-15.
^Kastler, Deanna L. (2010-07-22). "Cemeteries". Encyclopedia of San Francisco. Archived from the original on 2010-07-22. Retrieved 2022-10-14.