People attending the vigils in 100 cities, including Orlando, Fla., urged the U.S. Justice Department to bring civil rights charges against George Zimmerman, the neighborhood watch volunteer who was acquitted of murder in Martin's death, the Orlando Sentinel reported.
"The system did not work for Trayvon Martin. We are calling on the Department of Justice to take action," Temia Brinson, president of the National Action Network Central Florida Chapter, said outside the federal courthouse in Orlando where more than 500 people gathered.
Melinda O'Neal of Deltona, Fla., told the newspaper her sons could face a death similar to that of Martin.
"It makes me scared for them," she said. "Florida is a beautiful state, but the laws are screwed up."
"Today, all over the country, we're standing up," the New York Daily News quoted Sharpton as saying. "But nobody does it like New York."
Martin's father, Tracy Martin, led a gathering in Miami in singing "We Shall Overcome," the Sentinel said.
"This could be any one of our children," the Daily News quoted him as saying. "Our mission now is to make sure that this doesn't happen to your child.
"I will continue to fight for Trayvon until the day I die."
Members of the Congressional Black Caucus say they support an economic boycott of Florida after Zimmerman's not-guilty verdict.
Zimmerman was acquitted July 13 on second-degree murder and manslaughter charges in the February 2012 shooting death of Martin in Sanford, Fla.
The boycott, threatened by the Rev. Jesse Jackson, is seen as a means of overturning the state's stand-your-ground law, The Hill reported Saturday. Rep. Lacy Clay, D-Mo., said he supports the boycott as part of a "multi-pronged strategy" that includes legislation and getting laws overturned by the courts.
A drop-off in revenues "will get the attention of the powerful," he said.
Rep. Barbara Lee, D-Calif., said she would support "whatever it takes to get these stand-your-ground laws off the books."
Jackson said Thursday if the Justice Department does not file federal civil rights violation charges against Zimmerman, he would consider launching a boycott "to isolate Florida as a kind of apartheid state."
The nationwide rallies were intended to pressure the Obama administration to file federal civil rights charges against Zimmerman.
The National Action Network, founded by Sharpton, was one of the organizers of the vigils.