Most showed up at the 82-year-old landmark around 8 p.m. for a sentimental walk along the viaduct and took advantage of their last opportunity to take farewell photos before the bridge closes Wednesday.
Although fans were not there to protest, police were forced to step in and disperse large crowds out of concern for people's safety, LAPD officers said.
The growing number of people began to block traffic and when someone from the crowd set off a smoke bomb, officers ordered everyone to leave the area.
One person was arrested for disobeying police orders.
"It's a great feeling to be here and actually see this for ourselves because we're not going to get to experience it again," Christy Montoya, a Los Angeles resident, said.
The 3,500-foot concrete bridge that connects the downtown Arts District to Boyle Heights is expected to officially begin its demolition process Wednesday morning, although after the gathering, crews began to put up fences Tuesday night.
City officials have agreed to bring down the iconic structure because of "concrete cancer," an alkali-silica reaction that threatens the long-term integrity of the bridge.
A $449-million project for the new Sixth Street Bridge is expected to be completed in 2018 and opened in 2019. Officials said it will look similar to the original.
A 40-hour closure of the 101 Freeway has been set to enable safe demolition of the bridge, located over the freeway, beginning at 10 p.m. on Feb. 5.
The historic bridge, built in 1932, is arguably Los Angeles' most well-known bridge as it has been the scene of many Hollywood films, commercials and music videos.