(CNN) -- For many Americans across the country, Donald Trump's victory is an outcome they simply refuse to accept.
"Not my president," protesters chanted in rallies coast to coast.
Tens of thousands filled the streets in at least 25 US cities overnight -- with demonstrations outside Trump's properties across the country.
While most protesters were peaceful, dozens were arrested. At least three officers were wounded. And about 40 fires were set in one California city.
Here's a snapshot of the rallies across the nation:
New York: Thousands march outside Trump's home
About 5,000 people protested the real estate mogul's victory outside Trump Tower, authorities estimated. They included pop star Lady Gaga, a staunch Hillary Clinton supporter.
Their concerns ranged from policies, such as Trump's proposed plan to build a wall along the US-Mexican border, to the polarizing tenor of his campaign that they say stoked xenophobic fears.
"I came out here to let go of a lot of fear that was sparked as soon as I saw the results," protester Nick Powers said in New York. He said he feared Trump will support stronger stop-and-frisk policies that would put many people in prison. Powers said he was also worried that Trump's victory would embolden sexist views.
At least 15 protesters at Trump Tower were arrested Wednesday night for disorderly conduct, New York police said.
Oakland, California: 40 fires started
About 7,000 demonstrators filled streets in Oakland on Wednesday night -- and some turned violent.
Protesters hurled Molotov cocktails, rocks and fireworks at police. Three officers were injured, Oakland police spokeswoman Johnna Watson said.
Trash fires smoldered on a highway, and a downtown business was set ablaze. By Thursday morning, emergency workers extinguished about 40 fires.
"Throughout the evening, the large group splintered into smaller groups that began vandalizing numerous businesses in the downtown area," Oakland police said.
At least 30 people were arrested and 11 citations were issued for vandalism, assaulting officers, unlawful assembly, failure to disperse and possession of a firearm.
Three police cars from nearby Pleasanton were damaged, officials said.
A few miles away at Berkeley High School, about 1,500 students walked out of classes Wednesday -- one of numerous high school walkouts that occurred nationwide after the election.
"People are furious, not just at the results of the election but the rhetoric of Donald Trump," said Ahmed Kanna, an organizer for Social Alternative at Berkeley.
Chicago: 'We're taking many steps back'
In Chicago, activists marched down Lake Shore Drive -- an eight-lane expressway along Lake Michigan -- toward the Windy City's Trump Tower.
"I still can't believe I have to protest for civil rights," one sign read.
CNN's Ryan Young, who saw a few thousand people there, said many chanted vulgarities toward the president-elect.
"As a nation we thought we had come so far, but it seems like we're taking many steps back," one woman said. "We want to come together to change that."
Los Angeles: Trump effigy torched
More than 1,000 protesters rallied outside Los Angeles City Hall, including many young Latinos.