The conference, hosted by the white nationalist organization National Policy Institute, met inside the Ronald Reagan Building and International Trade Center downtown, a block from Trump's new International Hotel. NPI's leader is Richard Spencer, known for coining the term "alt-right" and promoting white supremacist views.
The event drew hundreds of protesters holding anti-fascist signs and yelling chants including, "No Donald Trump, no KKK, no fascist USA!" One held a sign reading "alt-wrong."
The group was generally peaceful until a man and a woman from NPI approached the group with a video camera and microphone, prompting protesters to yell "Nazis go home." The woman, who wouldn't give CNN her name but wore a badge saying "Emily," appeared to interview a protester, asking him if he is a "self-hating white person."
Another protester knocked the man's video camera, and a scuffle ensued between the two. A few other protesters entered the fray yelling "Die, Nazi, die," and the man from NPI reemerged with a bloody gash on his forehead. He declined to give his name.
Two protesters were handcuffed by police. CNN videotaped the incident.
Police later escorted the pair from NPI to a waiting ambulance while the rest of the protesters continued marching peacefully along Pennsylvania Avenue.
A group called Smash Racism DC posted a call to action on Facebook, encouraging people to "challenge" the NPI and "make noise, chant, and be generally disruptive."
"We confront, and do not ignore, oppressors," the website says
"Emily," who referred to the protesters as communists. said she is concerned about the decreasing white population in the United States but less so "now that Donald Trump is president."
Protester Carl Goldman said, "That's what they said in Nazi Germany, where my relatives grew up."
Demonstrators march in NYC
More than 500 people participated in a protest near Trump Tower in New York against the President-elect.
The protest was organized by New York City Councilman Jimmy Van Bramer, whose message was aimed at promoting peace, ending homophobia, and racism.
"The President-elect grew up in Queens, but it has different values from him," Van Bramer told CNN.
The protest was calm and controlled. Police were staggered alongside the protesters, riding motorcycles as the crowds chanted, "Say It loud, say it clear, immigrants are welcome here."