The decision was announced at 9:25 p.m. (6:25 p.m. Pacific Time) at the downtown courthouse in the St. Louis County seat of Clayton. Moments after the announcement, crowds across the U.S. took to the streets to protest the decision.
Although most demonstrations were peaceful, violence, fire and looting were reported in Ferguson and Oakland. In Los Angeles, marchers briefly shut down the 110 Freeway in downtown Los Angeles late Monday night.
The St. Louis County Police Department confirmed that shots were fired near the Ferguson Police Department. At least two police cars were set ablaze by protesters, and at least a dozen businesses were badly damaged or destroyed.
The department also tweeted that a Molotov cocktail was thrown at police. Smoke and eventually tear gas was being used to "break up unruly crowds," according to the @stlcountypd Twitter account. Reports of looting were also noted. Some in the crowd reportedly tried to stop others from taking part in vandalism and other violent reactions.
St. Louis County Police Chief Jon Belmar said police did not fire a shot during Monday night's protests, but that the protests were "probably much worse than the worst night we ever had in August" after Brown was killed. He said he "personally heard about 150 shots fired" during the course of the night. He said there were at least 29 arrests, and police recovered at least one .45 semi-automatic gun. At least 14 people were treated at local hospitals, according to ABC News.
A no-fly zone was ordered over Ferguson by the FAA, and went into effect at 11:15 p.m. in the area. At least 10 St. Louis-bound flights were diverted to other airports because of concern about gunfire being aimed into the sky over Ferguson.
President Barack Obama said in a live news conference after the announcement that he joins with Michael Brown's family in urging peaceful protests.
"We are a nation built on the rule of law, so we need to accept that this decision was the grand jury's to make," President Obama said.
The Aug. 9 shooting inflamed tensions in the predominantly black St. Louis suburb that is patrolled by an overwhelmingly white police force. As 18-year-old Brown's body lay for hours in the center of a residential street, an angry crowd of onlookers gathered. Rioting and looting occurred the following night, and police responded with armored vehicles and tear gas.
Photos from Ferguson, Missouri
The 12-person grand jury, composed of nine whites and three blacks, met weekly from Aug. 20 until Monday, Nov. 24. The grand jury deliberated for two days, said Robert McCulloch, St. Louis County Prosecuting Attorney.
The grand jury met on 25 separate days, reviewed 70 hours of testimony and 60 witnesses, according to McCulloch.
Hours of recordings were reviewed. Three medical examiners were consulted, along with forensics experts, as well as photographs and physical evidence.
"They are the only people that have heard and examined every witness and every piece of evidence," he said, adding that the jurors "poured their hearts and soul into this process."
Shortly after the announcement, authorities released more than 1,000 pages of grand jury documents, including Wilson's testimony.
Five potential indictments were presented to the grand jury, from first-degree murder to involuntary manslaughter. They were asked to consider whether there was probable cause to charge Wilson.
"While the grand jury proceeding in St. Louis County has concluded, the Justice Department's investigation into the shooting of Michael Brown remains ongoing," said U.S. Attorney General Eric Holder Monday night. "Though we have shared information with local prosecutors during the course of our investigation, the federal inquiry has been independent of the local one from the start, and remains so now."
The Brown family released a statement Monday night: "We are profoundly disappointed that the killer of our child will not face the consequence of his actions. While we understand that many others share our pain, we ask that you channel your frustration in ways that will make a positive change. We need to work together to fix the system that allowed this to happen. Join with us in our campaign to ensure that every police officer working the streets in this country wears a body camera. We respectfully ask that you please keep your protests peaceful. Answering violence with violence is not the appropriate reaction. Let's not just make noise, let's make a difference."
Security was enhanced around the courthouse, with barricades erected around the building and more than 20 Missouri state troopers assembled with rifles, 3-foot batons, riot shields and other equipment. Some nearby businesses boarded up their windows, just as many shops have already done near the site of Brown's death in Ferguson.
Several school districts called off classes for Monday and Tuesday, extending the Thanksgiving break. More than 15 districts cancelled Monday evening activities. Washington University closed a satellite campus in Clayton.
ABC News and The Associated Press contributed to this report.