Chicago is 2.4 times larger than Milwaukee.
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: 251 km2 calculated
Milwaukee is the largest city in the U.S. state of Wisconsin, the 30th most populous city in the United States, and 39th most populous region in the United States. It is the county seat of Milwaukee County and is located on the southwestern shore of Lake Michigan. Wikipedia