401 North Michigan occupies a site with several aspects of historical significance , both on a local and national scale . The site was originally settled by du Sable around 1779 , and operated as a personal residence and fur-trading post , forming the very beginnings of the city of Chicago . In 1803 , Fort Dearborn was built by the United States government immediately across the river , helping to protect the growing trading post from local Native American tribes . One year later in 1804 , John Kinzie bought du Sable 's property and occupied it until his death in 1828 . In 1849 , Cyrus McCormick moved to Chicago to set up a factory for his invention , the horse-drawn reaper , and purchased several lots on the former du Sable/Kinzie property , eventually developing a large factory complex . After this factory burned in the Great Chicago Fire in 1871 , McCormick moved his factory to the West Side . Even as Michigan Avenue was slowly rebuilt into the city 's premier street beginning in the 1920s , the site remained industrial in usage , and by 1961 , it had become a parking lot
Great Chicago Fire
Great Chicago Fire
Equitable Building (Chicago)