In New York, thousands filled streets in midtown Manhattan as they made their way to Trump Tower, Trump's gilded home on Fifth Avenue. Hundreds of others gathered at a Manhattan park and shouted "Not my president."
In Los Angeles, protesters sat on the 110 and 101 highway interchange, blocking traffic on one of the city's main arteries as police in riot gear tried to clear them. Some 13 protesters were arrested, a local CBS affiliate reported.
An earlier rally and march in Los Angeles drew more than 5,000 people, many of them high school and college students, local media reported.
A demonstration of more than 6,000 people blocked traffic in Oakland, California, police said. Protesters threw objects at police in riot gear, burned trash in the middle of an intersection, set off fireworks and smashed store front windows.
"I'm just really terrified about what is happening in this country," said 22-year-old Adriana Rizzo, who was holding a sign that read: "Enjoy your rights while you can."
Protesters railed against Trump's marquee campaign pledge to build a wall along the border with Mexico to keep out undocumented immigrants and other policies perceived as affecting people of color.
"I'm particularly concerned about the rise of white nationalism and this is to show my support against that type of thing," Rizzo said.
A representative of the Trump campaign did not immediately respond to requests for comment about the protests. In his victory speech, however, Trump said he would be president for all Americans, saying, "It is time for us to come together as one united people."
Earlier this month, after a Ku Klux Klan newspaper declared its support for Trump, his campaign rejected the support and said that "Mr. Trump and his campaign denounces hate in any form."
Hundreds of high school and college students walked out in protest in Seattle, Phoenix, Los Angeles and three other cities in the Bay Area, Richmond, El Cerrito and Oakland.
A predominantly Latino group of about 300 high school students walked out of classes on Wednesday morning in Los Angeles and marched to the steps of City Hall, where they held a brief but boisterous rally.
Chanting in Spanish, "The people united will never be defeated," the group held signs with slogans such as "Not Supporting Racism, Not My President" and "Immigrants Make America Great."
Many of those students were members of the "Dreamers" generation, children whose parents entered the United States with them illegally, school officials said, and who fear deportation under a Trump administration.
"A child should not live in fear that they will be deported," said Stephanie Hipolito, one of the student organizers of the walkout. She said her parents are U.S. citizens.
There were no immediate reports of arrests or violence.
Wednesday's demonstrations followed a night of protests around the San Francisco Bay Area and elsewhere in the country in response to Trump's political upset.
Demonstrators smashed storefront windows and set garbage and tires ablaze late Tuesday in downtown Oakland, California. A few miles away, students at the University of California, Berkeley protested on campus.
Police responded by throwing chemical irritants at the protesters, according to a Reuters witness.
Two officers were injured in Oakland and two police squad cars were damaged, Johnna Watson, spokeswoman for the Oakland Police Department told CNN.
In downtown Chicago, an estimated 1,800 people gathered outside the Trump International Hotel and Tower, chanting phrases like "No Trump! No KKK! No racist USA."
Chicago police closed roads in the area, impeding the demonstrators' path. There were no immediate reports of arrests or violence there.