Chicago is 4.1 times larger than Oakland, California.
Area: 608 km2 calculated
Chicago is the third most populous city in the United States, after New York City and Los Angeles. With 2.7 million residents, it is the most populous city in both the U.S. state of Illinois and the American Midwest. Wikipedia
Area: 150 km2 calculated
Oakland is a major West Coast port city in the U.S. state of California. The Port of Oakland is the busiest port for San Francisco Bay and all of Northern California. Wikipedia