Thousands of cheering onlookers clustered along downtown bridges as members of Chicago Journeymen Plumbers Union Local 130 began dumping containers of dye into the river from motorboats Saturday morning. The annual tradition began at 9:30 a.m. and immediately preceded the St. Patrick's Day parade.
The union has done the dyeing since 1962. Organizers had feared that large chunks of ice would impede the process, but recent warm temperatures kept the river clear. The hue typically lasts about six to 12 hours.
Here, a woman pauses for a selfie with the newly-green Chicago River.
Paul Beaty / AP
Jim Young / Reuters / Landov