North Chicago, industrial city (1990 pop. 34,978), Lake co., NE Ill.; inc. 1909. Its economy is closely intertwined with the neighboring city of Waukegan, which has a harbor on Lake Michigan. Pharmaceuticals, medical diagnostic-testing equipment, chemicals, steel, and automobile parts are among the many manufactures. A sit-down strike at a steel plant there in 1937 led to a U.S. Supreme Court decision (1939) ruling such strikes illegal. Naval Station Great Lakes, the U.S. navy's main training center for naval recruits, is adjacent to the city.