In addition to the businesses damaged, 17 people were arrested and four police injured, although all had been released from hospital, Flynn said.
The confrontation was sparked by the police's fatal shooting of Sylville K. Smith, a 23-year-old black man, when he was trying to flee from two police officers who had stopped his vehicle.
Milwaukee Mayor Tom Barrett said the new 10 p.m. curfew for teenagers would stay in effect as long as it was necessary.
People living on the north side are far more likely to live in poverty, to be incarcerated or to be out of work than those in the city overall or the metro area, according to a University of Wisconsin-Milwaukee report.
Milwaukee officials also announced that Sherman Park, the site of the shooting, would be closed from 6 p.m. until 6 a.m.
The incident comes amid renewed anger over the fatal shootings of several young African Americans by police around the United States in recent weeks.
At least seven officers were wounded, including some who were hit by rocks and bricks, police Chief Edward Flynn said.
Protesters also lit fire to vehicles, smashed squad cars and injured several law enforcement officers by throwing concrete and other objects. The shooting is under investigation.
Ninah Jackson, who said she is 13 years old, added, "There are some other names there too, but I can't say them".
But the body cam footage showed that Sylville K. Smith (whose Facebook page has images of his pointing guns at a camera) was holding a gun and pointing it at the officer when he was shot and killed. Smith was carrying a loaded gun stolen from Waukesha with 23 rounds.
Flynn has said Smith ran from a auto after it was stopped for what authorities described as suspicious behavior.
Police Chief Edward Flynn says 23-year-old Sylville Smith ran from a vehicle after it was stopped for what authorities described as suspicious behavior.
On Sunday morning, the Milwaukee Police Officers Association published a statement on Facebook calling demonstrators who had destroyed property "terrorists" who "must be held accountable", and Wisconsin Gov. Scott Walker activated the National Guard.
Some community leaders also have preferred not to publicize the issues, said state Sen.
Reached by phone, party co-founder Carl Dix said he wasn't in Milwaukee but confirmed that several party supporters from Chicago traveled the 90 miles north to protest against police, whom he blamed for both Smith's death and the subsequent violent protests.
Authorities here struggled into Monday to maintain order in part of Wisconsin's largest city, which was gripped by unrest after a police officer killed an armed man on Saturday.
"I can't look my brother in the eye and say, 'I love you".
Two officers suffered from glass fragments in their eyes after a rock went through the windshield of their squad auto, Flynn said. Police are concerned for his safety, Flynn said.
The police officer who shot Smith is a 24-year-old, six-year veteran of the Milwaukee Police Department, though he had been an officer for just three years, according to Flynn. But, I know there needs to be a police service, there needs to be protection and there needs to be a stop to the unrest and she would be able to do that and knowing that she'll be willing to go for those who aren't able to protect themselves in these communities.
"There is a curfew that will be more strictly enforced tonight for teenagers", Barrett said.
Police say the man who was shot Saturday was fleeing from police and had turned with a gun in hand toward the pursuing officer, who was also black.