The City of Chicago takes St. Patrick's Day very seriously. Celebrations occur even before the actual date. Today at 10:45 a.m., The Chicago River was dyed green to signify the beginning of St. Patrick's Day festivities. At noon the downtown St. Patrick's Day parade will commence starting at Balbo and Columbus Dr.
Dying the river is a debated subject. It has been done since the early 1960's. It is dyed by a pipefitter's union who uses fluoresein dye which is supposedly harmless, although some people question that fact.
However, this day most likely is the day that more people come down to see the river than any other day of the year. Although it is drizzling rain today it is one of the warmest days for the St. Patrick's Day parade in recent years so expect a huge crowd. Public transportation is highly recommended.