The crowd chanted anti-Nazi slogans and waved signs condemning white nationalism as it made its way in downtown Boston on Saturday, Xinhua news agency reported.
A so-called "free speech" rally by far-Right groups had been scheduled to run until 2 p.m. (1800 GMT), but a half-hour before that police escorted its participants - whose numbers appeared to be in the dozens - to safety past a throng of anti-racism protesters.
Officials estimated a turnout of 40,000 demonstrators.
A 32-year-old woman, Heather Heyer, was killed and several people were injured when a man crashed a auto into a crowd of counter-protesters at last Saturday's rally.
"It was attractive to see thousands of people across the United States of America come together today to peacefully denounce bigotry, racism & anti-semitism", she tweeted Saturday, following numerous demonstrations across the country against white supremacy.
Just in case anyone in the White House or conservative media tries to demonize these courageous people who stood up against racism, protester Danielle Williams said, "What brought me out here today?" Most arrests were for charges of disorderly conduct, with a few battery and assault charges. "No KKK. No racist USA" and "Americans against hate".More news: Bonnie Tyler Total Eclipse of the Charts ... During Solar Eclipse
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Mr. Trump went on to say last week that there were "very fine people" who had attended the rally - remarks that were a follow-up to his initial statements on the violence.
The former head of homeland security, meanwhile, said that top Trump administration officials such as defence secretary Jim Mattis should "absolutely not" quit, if they were considering it, since they're needed to "right the ship".
The Boston protests came one week after the Charlottesville white nationalist rally last weekend that erupted in violence and left one woman dead. He later issued a specific condemnation of the white nationalists, but continued to equate their actions with those of the counterprotesters.
Some of Trump's comments, criticising "alt-left" protesters as "very, very violent", came on August 15th with Mnuchin standing by the president's side in the lobby of Trump Tower in NY. "I want to thank all the people that came out to share that message of love, not hate". To fight back on anti-Semitism.
Others carried a large banner that read: 'SMASH WHITE SUPREMACY'. The US needs people such as Kelly, Mattis and national security adviser HR McMaster "to right the ship", he said. The march was otherwise described as largely peaceful.