WHERE IT HAPPENS
The Chicago River is dyed green the Saturday before each St. Patrick's Day -- unless the holiday falls on a Saturday, which it does this year. The dyeing process takes place between Wabash Avenue and Columbus Drive. Spectators can watch the boats from both sides of the river between these bridges.
HOW IT BEGAN
Mayor Richard J. Daley is credited not only with reviving Chicago's St. Patrick's Day parade, but also proposing the idea of greening part of Lake Michigan to celebrate the holiday. It was his boyhood friend and Chicago Plumbers Union business manager Stephen M. Bailey who suggested dyeing the Chicago River instead. The Chicago River would run green for the first time in 1962 (the same year the photo below was taken), one year after Savannah, Ga., unsuccessfully tried to dye its river green for the Irish holiday.
HOW THE CHICAGO RIVER IS DYED GREEN
According to Tom Rowan, head of the crew
Prep work: Early in the morning, the crew arrives at a city boat slip on the North Branch of the river. Everyone wears clothes and shoes they don't mind getting dirty and a white paper smock over their clothes.
On the water: The crew hops aboard two small motorboats donated by volunteers. The larger boat, at approximately 18 feet, has a crew of four. The smaller boat, a 12-footer, has two people.
A 9 a.m. start: The larger boat is responsible for dyeing the river, which begins when it arrives under the Michigan Avenue bridge near Wacker Drive.
Kitchen secret: Three men use flour sifters to dump about 40 pounds of an environmentally friendly orange powder into the river. The fourth drives the boat. The formula for the powder, which turns the water bright green when it hits, is top-secret.
Powder spread: The smaller boat "chases" the larger boat and churns up the water, which helps disperse the powder across the river. Traveling the river between Wabash Avenue and Columbus Drive, the large boat snakes across the waterway dumping powder.
Green sheen: It takes about 45 minutes for the river to turn completely green. Depending on which direction the wind is blowing, the water can stay green for up to a few days.
Sources: As told to the Chicago Tribune by Tom Rowan and Michael Butler, whose families have been involved in dyeing the Chicago River since 1962, Chicago St. Patrick's Day Parade Committee, Choose Chicago, Tribune archives