Demonstrators returned on Tuesday night to the riot-scarred streets of the St Louis suburb, but with hundreds of additional troops standing watch over neighbourhoods and businesses, the protests had far less destructive power than the previous night.
But officers still used some tear gas and pepper spray, and demonstrators set a squad car on fire and broke windows at City Hall.
Protests were also reported in 12 other US cities: Philadelphia, Seattle, Albuquerque, New York, Cleveland, Los Angeles, Oakland, Minneapolis, Atlanta, Portland, Chicago and Boston.
The demonstrations were mostly peaceful, but rioting broke out in Oakland, California.
In Los Angeles, 130 protesters were arrested for disorderly conduct, the LA Times reported.
As the tension in Ferguson eased somewhat, officer Darren Wilson broke his long public silence, insisting on national television that he could not have done anything differently in the confrontation with Michael Brown.
The decision announced on Monday means Mr Wilson faces no state criminal charges over the August 9 shooting in Ferguson, which reignited debates over relations between police and minority communities, even in cities far from Ferguson.
The toll from Monday’s protests – 12 commercial buildings burned to the ground, plus eight other blazes and a dozen vehicles torched – prompted Missouri governor Jay Nixon to send a large contingent of extra National Guard state militia troops.
The governor ordered the initial force of 700 to be increased to 2,200 in hopes that their presence would help local law enforcement keep order in Ferguson.
“Lives and property must be protected,” Mr Nixon said. “This community deserves to have peace.”
Guard units protected the Ferguson Police Department and left crowd control, arrests and use of tear gas to local officers. In one commercial area this morning, a soldier was stationed at every few store fronts, and some were on rooftops.
Forty-five people were arrested, most for failure to disperse. Outside police headquarters, one woman was taken into custody after protesters hurled what appeared to be smoke bombs, flares and frozen water bottles at a line of officers. Several other protesters were arrested after defying police instructions to get out of the street or out of the way of police vehicles.
Protesters threw rocks, tent poles, and bottles – some containing urine – at officers.
Some streets that had been over-run the previous night were deserted, except for the occasional police cruiser or National Guard vehicle.
During an interview with ABC News, Mr Wilson said he has a clean conscience because “I know I did my job right”.
The 28-year-old had been with the Ferguson police force for less than three years before the shooting.
He told ABC that the shooting was the first time he had fired his gun on the job.
Asked whether the encounter would have unfolded the same way if the teenager had been white, Mr Wilson said yes.
Mr Wilson said in his grand jury testimony that he feared for his life during his confrontation with Mr Brown, which he blamed on the teenager, saying the theft suspect reached through his driver’s side window, hit him in the face, verbally abused him and tried grabbing his gun. Mr Wilson then got off a shot that went through Mr Brown’s hand, the only bullet that hit him at close range.
Mr Wilson told ABC he felt like it was his duty to chase Mr Brown after the confrontation at his police vehicle. When asked about witness accounts that Mr Brown at one point turned towards Mr Wilson and put his hands up, he responded “that would be incorrect”.
Mr Brown fell to the ground about 153ft from Mr Wilson’s vehicle, fatally wounded by the last of the seven bullets that struck his body.
Public attention to the killing has frequently focused on the fact that Mr Brown was unarmed. But whether or not he had a weapon makes little difference under Missouri law, which says police can act with deadly force when they believe it is necessary to arrest a person who may “endanger life or inflict serious physical injury”.
Lawyers for the Brown family vowed to push for federal civil rights charges against Mr Wilson. They said the grand jury process was rigged from the start to clear the officer.