Power has been restored to nearly all -- 99 percent -- of the customers who who knocked out during Tuesday's storms, Commonwealth Edison reported Friday night.
Just 4,000 customers remain in the dark, the utility said, down from a high of roughly 440,000 customers three days ago.
More than 800 crews, including 160 brought in from other states, worked 16-hour shifts to get those customers back online.
The company said it repaired or replaced more than 100 transformers, 100 poles, 240,000 feet of overhead cable and 12,000 feet of underground cable, since the storm struck.
Tuesday's outages were among the most widespread with which the utility has dealt. The worst was an Aug. 23, 2007 incident when 634,000 customers lost power.
The National Weather Service confirmed Wednesday that much of the damage done in the summer solstice storm was done by two tornadoes, one with speeds up to 100 mph.