Protests in Ferguson, elsewhere muted after two nights

In and around Ferguson itself, some 2,200 National Guard troops called out by Missouri Governor Jay Nixon were backing up local police.

"The ramped-up presence and action of the Missouri National Guard has been helpful," Nixon said on Wednesday after facing criticism for not deploying enough troops in the immediate hours after the grand jury's decision was announced Monday evening.

About a half-dozen clergy members, wearing orange vests, also milled about on Wednesday night among the protesters, most of whom stood quietly in the snow, as passing motorists occasionally honked their horns in support.

Tensions between police and black Americans have simmered for decades, with many blacks feeling the U.S. legal system and law enforcement authorities do not treat them fairly.

In Washington, President Barack Obama has tried to keep a lid on the anger. He remained cautious in his comments in the immediate aftermath of the Ferguson shooting, but has been more expansive in recent days including remarks at the White House after the grand jury's decision. On Monday he said deep distrust exists between police and minorities and that "communities of color aren't just making these problems up."

St. Louis police said three people were arrested at a protest near City Hall on Wednesday in which activists staged a mock trial of Wilson.

Ferguson's 21,000 population is mixed, with 63 percent of the residents African-American and 34 percent white, according to 2010 US Census data. Ferguson's mayor, James Knowles, is white, as are most of its city council members.

A 2013 state attorney general's report found more than 85 percent of motorists pulled over in the city are black, and the arrest rate among blacks is twice that among white residents.

The Justice Department has been investigating whether to bring federal civil rights charges against Wilson and the Ferguson police department.

"The sad fact is that it brings up issues that we've been struggling with in this country for a long, long time," said Matthew Green, an associate professor of politics at the Catholic University of America. "These are not problems and issues that are going to get resolved by one president in the remainder of his term."