Question: The Downtown Oakland Historic Districit is part of what California County?
Sentence (from "Oakland, California"): A major West Coast port city, Oakland is the largest city in the East Bay region of the San Francisco Bay Area, the third largest city overall in the San Francisco Bay Area, the eighth largest city in California, and the 45th largest city in the United States, with a population of 419,267 as of 2015 .
Relevant evidence: No