Biden became the first U.S. president to officially call the killings a genocide on Saturday, fulfilling a campaign promise and a longstanding lobbying effort by the Armenian-American community.
"The American people honor all those Armenians who perished in the genocide that began 106 years ago today," Biden said in a statement. "We affirm the history. We do this not to cast blame but to ensure that what happened is never repeated."
Crowds gathered near Cedars-Sinai Medical Center on Wilshire and La Cienega boulevards, waving Armenian and American flags.
A similar rally was also held outside the Turkish Consulate on 8500 Wilshire Blvd.
The massive crowd chanted and waved flags and many said they were happy that Biden followed through on his campaign promise.
"Turkey has never admitted it. Turkey has killed 1.5 million Armenians in cold blood. And to this day, 106 years later, parts of the world, including Turkey and Azerbaijan, do not recognize what happened. We need justice, we need it now," said demonstrator Hayk Yengibaryan
Biden formally recognizes atrocities against Armenians as genocide
Video from AIR7 HD showed demonstrators spilling out onto Wilshire after initially remaining on sidewalks on each side of the street, where crowd-control barriers were set up.
More than 200,000 people of Armenian descent live in Los Angeles County, making the Southland home to the largest Armenian community outside of Armenia.
Later Saturday, Glendale plans to host its 20th annual Armenian Genocide Commemoration Event in a virtual format. The ceremony will be livestreamed at 7 p.m. on the city's Facebook and Instagram pages, as well as its YouTube channel.
City News Service contributed to this report.