In a court filing, prosecutors said they plan to focus on "the core group that we believe is most responsible for the destruction and violence that took place on Inauguration Day."
The decision comes about a month after a D.C. jury acquitted the first six people to go to trial on rioting charges stemming from the Jan. 20, 2017, celebration. Lawyers for those defendants argued they were lawfully protesting while others in the group peeled off to vandalize businesses and vehicles.
The prosecutors' decision, announced late Thursday, was applauded by supporters of the protesters who have argued the government overreached in its response.
Oliver Harris, 28, of Philadelphia, who was one of the six protesters acquitted last month, said the dismissal is "a victory for those whose charges were dropped, but we now also have to redirect our support for those 59 persons whose charges are remaining."
In all, 234 people were charged in connection with the riots. Twenty have pleaded guilty, and prosecutors previously dropped cases against another 20.
Trials for the remaining defendants were set to proceed through the year, with the next set for March.
During the first trial last month, prosecutors said the six defendants were among a group that cut a violent swath through 16 blocks of the city, smashing businesses' windows, tossing newspaper boxes into the street and damaging a limousine. Authorities tallied the damage at more than $100,000.
The group used "black-bloc" tactics, prosecutors said, wearing dark clothes and hiding their faces with masks and goggles so it would be harder for authorities to identify them while they participated in violence.
While the prosecutors had no evidence showing the six defendants directly caused damage, they argued the whole group essentially provided cover to the vandals.
Judge Lynn Leibovitz dismissed the most serious charge against the six, finding there was no evidence they urged others to riot. Jurors later acquitted the defendants on the remaining charges, saying after trial that prosecutors failed to prove the six actually participated in the riots, as opposed to being part of the group that was peacefully demonstrating.
The acquittals left legal observers and defense attorneys wondering whether prosecutors would pursue the remaining cases. At the time, the U.S. attorney's office promised to press on.
But on Thursday, prosecutors said they would focus on the 59 defendants who they believe planned or caused damage — or those evidence shows conspired to use black-bloc tactics.
"In light of the legal rulings by the court and the jury's verdicts in the first trial of these cases, the government has decided to proceed with all of the pending charges set forth in the superseding indictment," Assistant U.S. Attorney Jennifer Kerkhoff, the lead prosecutor on the case, wrote in the filing.
The case follows one of the largest mass arrests for vandalism in the city, and authorities spent months mining for evidence. Authorities confiscated the cellphones of the defendants to examine text messages and videos. And prosecutors sought court orders for Internet records, including website visits and Facebook accounts, in hopes of securing evidence to support their contention protesters planned to participate in a violent demonstration. The searches were challenged by attorneys and civil liberties groups as violating the rights of the users.
Defense attorney Betty Ballester said she is looking forward to telling her client, Kenneth Delacruz, 22, of New York, that his case was dropped.
"This is such good news. I haven't stopped dancing," she said. "The prosecution had to rethink things after that first trial."
Perry Stein and Ellie Silverman contributed to this report.