What to Know Thousands are expected at the planned peace march this weekend, which aims to shut down part of the Dan Ryan Expressway.

Illinois State Police have warned any pedestrians entering the expressway will "face arrest and prosecution."

Mayor Rahm Emanuel Friday said he supports the expressway shutdown, calling it an "important march."

NOTE: NBC Chicago will have live coverage from the Dan Ryan Saturday morning. Watch live here.

Hundreds of protesters marched onto the Dan Ryan Expressway Saturday as they called for an end to Chicago's violence.

But why shut down one of Chicago's busiest roadways?

Rev. Michael Pfleger, who helped organize the march, wrote on Facebook "civil disobedience is to say we will interrupt Business as Usual to Demand these issue be Addressed!!!"

He wrote the expressway shut down aims "to Force the City to stop ignoring this violence."

Police threatened arrests and argued the march could be detrimental to the very communities protesters aim to help.

What is it for?

Organizers said they are calling for five things: Excellent schools, economic development, national gun legislation, job opportunities and resources for our communities. Pfleger has said the march is in protest to the city's violence.

"This is not about just a march," Pfleger said at a press conference, pointing to news of 61 children struck by gunfire so far this year. "This is not about just an interruption of traffic. This is about the violence in the city of Chicago."

The massive crowd marched onto the expressway just after 10 a.m. chanting "shut it down right now."

Multiple northbound lanes were closed down at 79th Street and authorities also warned drivers that the exit ramp at 76th was also blocked.

But despite plans to "shut down the Dan Ryan," Illinois State Police said officers will create a boundary to allow the protesters one lane plus the shoulder.

"The marchers will have access to the grassy area, shoulder and first lane – in cooperation with their police escorts. We all intend to live up to that agreement," ISP said in a statement.

Who is involved and how many people are expected?

Rev. Michael Pfleger has been arguably the biggest proponent of the march, but the event has been organized by ChicagoStrong, "a coalition of students from Chicago committed to being part of the solution to end gun violence in our city."

Pfleger said up to 3,000 protesters were expected Saturday. Groups from Evanston, Naperville and other suburbs were expected to take busses into the city to attend the event.

Rev. Jesse Jackson and other community leaders also support the protest.

Who says what?

While Illinois State Police have warned arrests would be made for those entering the expressway, Chicago police said the department will be on hand to assist with crowd safety and traffic control.

CPD has cautioned the event could have a negative impact on some of the city's most violence-plagued communities.

“The very thing that they’re trying to accomplish — stop violence and stop shootings — has the potential to actually escalate because we’re pulling police officers out of the neighborhoods where we need them in order to escort the protesters down the expressway,” First Deputy Superintendent Anthony Riccio told reporters after a City Hall hearing last week, the Chicago Tribune reported.

Police said they strongly discourage the protest at this location and said they met with Pfleger to discuss the dangers of doing it, from causing potential hazards for traffic on the expressway to putting the protesters themselves at risk.

Pfleger was quick to respond when asked about the reallocation of police for the march.

"I don't work for the police department, but let me offer them some advice," he said. "If they say doing this will pull officers from the most needed neighborhoods in the city of Chicago, then pull them from the North Side."

Pfleger and others noted major arteries are often shut down for public events and construction.

"If the president of the United States was to come to Chicago today, law enforcement would immediately be pulled and the entire expressway would absolutely be shut down without negotiation, without conversation and without fail," Pastor Chris Harris said, "to protect one man who ironically has not done anything currently to save the lives of the thousands who have been murdered, shot or wounded in this great city of Chicago."

Mayor Rahm Emanuel Friday said he supports the expressway shutdown, calling it an "important march."

"It highlights gun control and economic opportunity. They are going to raise awareness... I want to widen everybody’s lens... the march is an important component of that," Emanuel said.