From the plaque on the statue:
This statue was given to Supervisor Kenneth Hahn by sculptor Robert Merrell Gage and was placed at this location by order of the Board of Supervisors on September 13, 1988. The unveiling was held on April 24, 1989.
The base of the statue also includes texts of the Emancipation Proclamation, and of the Gettysburg Address.
Excerpt from Donald Durman's He Belongs to the Ages, 1951.