The $7 billion project is designed to transform development and investment around the United Center.
Mayor Johnson, Cook County Pres. Preckwinkle speak ahead of 1901 Project groundbreaking
Phase One includes building a new music venue, hotel and parking garage.
Among those attending the ceremony were Bulls President Michael Reinsdorf and Blackhawks CEO Danny Wirtz.
A Chicago City Council Committee last month approved a $55 million tax break for the project.