Dozens of protesters tied up traffic in the West Loop Monday evening as they marched and rallied against the union that represents thousands of rank-and-file Chicago police officers.

About 70 people gathered in Union Park near the corner of Washington and Ogden Avenue at 4 p.m. After a few speeches, they crossed Ogden — with the escort of dozens of police officers — to continue the rally and speeches outside the Fraternal Order of Police Lodge at 1412 W. Washington Blvd.

Among the speakers outside the lodge was Anthony Clark, a history teacher at Oak Park and River Forest High School who was suspended earlier this year after allegedly helping students stage a walkout on the anniversary of Trayvon Martin’s death. He had earlier been the target of racist graffiti found near the school.

“This is an institution built upon white supremacy,” Clark said of police. “Built upon it. And they say police officers and police departments are supposed to serve and protect, but who the f— are they protecting? The system.”

A representative for the FOP declined to comment on the protest Monday evening.

Monday’s march and rally were spurred in part by the FOP’s criticisms of Cook County State’s Attorney Kim Foxx and her office’s decision last month to drop criminal charges against “Empire” actor Jussie Smollett, who had been arrested for allegedly faking a hate crime against himself.

After the charges were dropped, the FOP organized a rally to call on Foxx to resign. While they were met with counter-protestors, some men from groups with ties to white nationalists also showed up for the rally. FOP officials said they had no idea the men would be present.

Ten officers guarded the doors of the FOP Lodge Monday and vehicle traffic was blocked off on Washington during the speeches. Afterwards, the group marched back to Union Park. A dozen protesters, though, continued to block westbound traffic on Ogden and were arrested after several warnings to leave the street from a Near West District lieutenant.

A few obstructing traffic arrests happening now. This seems part of the plan, though. Organizers said at the start that several attendees had said they were prepared to be arrested. pic.twitter.com/MamYY13OAl — Sam Charles (@samjcharles) May 6, 2019

Before the march began, an organizer told attendees that others in the group were OK with being arrested. After the 12 were taken to the Near West station on Blue Island Avenue, a representative for the arrestees could be seen smiling and shaking hands with the lieutenant who warned them to get out of the street.