Protesters were arrested early Friday morning for interfering with traffic. Many were also accused of vandalizing public property, including buildings and patrol vehicles.
Metal barriers were then placed surrounding LAPD headquarters as law enforcement prepared for more demonstrations.
LAPD officials said sometime between midnight and 3 a.m., an officer from the department was injured at Spring and 2nd streets during an arrest. Details on the extent of the officer's injuries were not released.
"We did have one officer when trying to take someone into custody - that officer was transported to a local hospital. At this time, he's in stable condition and he's expected to be released later today," said Sgt. Barry Montgomery of the LAPD.
The aftermath - graffiti and damage - was seen in several parts of the downtown L.A. area Friday morning.
"There's going to be a lot of graffiti. There's going to be some damage to some buildings, some vehicles, and I will tell you, even to the psyche of the city itself," said LAPD Sgt. Jack Richter. "It's really unfortunate that individuals feel they have to damage other people's property in order to voice their opinion on a political election."
The crowd of protesters Thursday night started at a modest size of 50 to 75 rallying at Los Angeles City Hall. They then started marching through the streets of downtown as one group merged with another, and the crowd grew to several hundred as they continued walking.
They held anti-Trump signs and chanted slogans that included: "We reject / the president-elect" and "Not my president." Some also chanted "Hands up, don't shoot" when confronted by officers.
There were scattered reports of people throwing rocks and bottles at officers, and some police cars were tagged with graffiti.
The Los Angeles protests were among many held around the country in the wake of Trump's election, including Portland, Oakland, Minneapolis and even Vancouver, Canada.
The president-elect blasted protesters on his Twitter account: "Just had a very open and successful presidential election. Now professional protesters, incited by the media, are protesting. Very unfair!"
Just had a very open and successful presidential election. Now professional protesters, incited by the media, are protesting. Very unfair!— Donald J. Trump (@realDonaldTrump) November 11, 2016
But early Friday, the billionaire businessman changed his reaction to a more positive one. He tweeted: "Love the fact that the small groups of protesters last night have passion for our great country. We will all come together and be proud!"
Love the fact that the small groups of protesters last night have passion for our great country. We will all come together and be proud!— Donald J. Trump (@realDonaldTrump) November 11, 2016
Earlier in the day Thursday, a group of anti-Trump protesters shut down the 10 Freeway near California State University, Los Angeles, in Boyle Heights.
Large crowds also gathered at the University of Southern California, University of California, Los Angeles, and in South Gate to protest Trump.
Students at USC were seen at one point holding hands to form a human chain.
MORE: Police fire rubber bullets at anti-Trump protesters in Santa Ana; 10 arrested
At UCLA, hundreds gathered with signs and shouted as they marched across the campus.
Twenty-eight people were also arrested overnight Wednesday as thousands took to the streets of downtown L.A. and blocked traffic on the 101 Freeway in protest of Trump.
LAPD Chief Charlie Beck issued a statement on Twitter in response to the protests.
The statement read in part: "Your 1st amendment right to freedom of speech is a cherished privilege that should be exercised. However, destruction of property and vandalism will not be tolerated. Exercise your rights responsibly and respect our city."
1/3..Your 1st amendment right to freedom of speech is a cherished privilege that should be exercised. However..— Chief Charlie Beck (@LAPDChiefBeck) November 11, 2016
2/3..destruction of property and vandalism will not be tolerated. Exercise your rights responsibly and respect our city.— Chief Charlie Beck (@LAPDChiefBeck) November 11, 2016