Wisconsin passed a law stripping public employee unions of collective bargaining rights and local protesters say it could happen in Southern California.
Union members and their allies gathered at the Los Angeles Convention Center and marched onward to Pershing Square in hopes of sending out a message that collective bargaining rights cannot be taken away from unions.
A controversial bill in Wisconsin has pitted Democrats and Republicans against each other, limiting collective bargaining rights of government employees.
The bill was signed into law by Republican Wisconsin Gov. Scott Walker. Legislators and governors in several other states are seeking to adopt similar laws, citing budget problems.
The bill was blocked by a judge but published online on Friday by the state's Legislative Reference Bureau, which essentially means it would go into effect.
Ultimately, though, the state Supreme Court will likely decide the law's fate. A state appeals court earlier in the week asked the Supreme Court to take up one of several lawsuits challenging its approval of the bill.
The president of Professional Firefighters of Wisconsin came to California for Saturday's rally, and though firefighters and law enforcement officials are exempt from the bill, Mahlon Mitchell said he came to support all workers and protect the rights of the middle class.
"I think the future of unions are in trouble. They're in danger. But this is not just about unions. This is about the middle class. It's about a movement that the middle class has to stand up for themselves, because if we don't stand up now, we'll continue to have more attacks later," said Mitchell.
Marchers were making their way through downtown before reaching Pershing Square, where a rally was planned with music and speakers.
The Associated Press contributed to this report.