CHICAGO (CBS) — More than 1,000 immigration rights activists have begun marching along Chicago streets from the Near West Side to Federal Plaza downtown, as part of an annual May Day rally calling for easing immigration laws.

Protesters gathered in Union Park at Lake Street and Ashland Avenue around 2 p.m. before marching east to the memorial for the Haymarket labor riot near Randolph and Desplaines streets, then to Federal Plaza in the Loop for a rally.

READ MORE: Chicago Weather: Winter Weather Advisories In Effect; Snow Arrives For Monday Morning Commute

The crowd grew larger as the protesters marched east, stretching at least two blocks long by mid-afternoon, with the street packed sidewalk to sidewalk. Police escorted the group, blocking off streets to allow them to march freely to the Loop.

U.S. Sen. Dick Durbin spoke at the rally at Federal Plaza.

READ MORE: MISSING: Felicity Barr, 16, Last Seen In Aurora

The protest march and rally carry special significance this year, after a group of U.S. senators introduced bipartisan legislation to give legal status to some 11 million immigrants living in the U.S. illegally.

MORE NEWS: Melissa Ortega, 8-Year-Old Girl Killed In Little Village Shooting, Had Just Emigrated From Mexico

Organizers said they expected 2,000 to 5,000 people to attend the rally, but crowd estimates were not immediately available as the protesters were marching to downtown.