California and Los Angeles were close enough to "gold". This one was the one chosen. I can give you the actual date, etc., once I find my copy of Southern California Gardens, by Victoria Padilla. IIRC, there is even a photo of the actual decree.
For more information on the rose, see The Vintage Rose (The Friends of Vintage Roses), Nov/Dec 2015 issue online.--Oops. Seems that issue is no longer online. Well, here's the wording of the Calif. State Assembly's Resolution #99 (1949): "WHEREAS, it is fitting that this rose, commemorating the State's one hundredth birthday, be designated the California State Rose, now, therefore, be it resolved by The Assembly of the State of California that the California Centennial rose bred by Mr. Fred H. Howard is officially designated the California State Rose."
