Sanders, who is seeking the 2020 Democratic nomination, visited Chicago as part of a weekend of campaign kick-off events.
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"Real change never takes place from the top on down, it always takes place from the bottom on up," the 77-year-old Sanders told the crowd.
During the open and free rally, Sanders talked about offering free college and Medicare for all, as well as how his time at the University of Chicago shaped his world view.
"We have begun the political revolution and now we are going to complete it," said Sanders, who has launched his second bid for the presidency.
Sanders is a graduate of the University of Chicago, where he helped lead student protests against segregated housing and police brutality during the height of the Civil Rights Movement, according to a press release from his campaign.
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Sanders, who spoke for about an hour and 20 minutes, will face a large and diverse field of candidates seeking to unseat Donald Trump.