She was first elected in November 2010 as President of the Cook County Board, the executive branch of Cook County government, and became the first woman elected to this position.
She was previously a five-term alderman in the Chicago City Council, representing Chicago's 4th ward.
In her first four terms in office as alderman, she emerged as the council's prominent defender of affordable housing.
Among other issues, she is known for championing the controversial sweetened beverage tax, sponsorship of living wage ordinances, concerns about the costs and benefits of the city's Olympic bid, and her strong stance against police brutality and excessive force.
In September 2018, Preckwinkle announced her candidacy for Mayor of Chicago to succeed Rahm Emanuel in the 2019 election.
She, along with Lori Lightfoot, advanced to the runoff election on April 2.
She was defeated in the April 2 election by Lightfoot.