It is the 100th anniversary of the Chicago Union Stockyards fire, which killed nearly two dozen firefighters.
An electrical fire in the stockyards spread quickly, killing 21 Chicago firefighters on December 22, 1910.
Until the September 11th terrorist attacks, it was the largest loss of life of firefighters in any single incident.
Chicago's Wall of Remembrance for the loss of life that day includes the names of the 21 who lost their lives. The names of more than 500 other Chicago firefighters who died in the line of duty are also etched on the wall. No one wanted to add two more names.
A memorial service took place Wednesday morning at the wall and monument.
"We were reading the 21 names off in a roll call, when we heard the radios of the two fire engines that were aside the monument, you could hear the radio blaring 'mayday, mayday, mayday.' Mayday only means one thing: firefighter down," said Bill Cosgrove, author of Chicago's Forgotten Tragedy.
On that day 100 years ago, a stockyards night watchman discovered fire in the basement of one of the packing houses. When engines arrived at the scene, they found boxcars paralleling the long loading dock and a canopy above. Below-freezing temperatures had frozen the hydrants. Multiple units arrived to help.
"Suddenly, six stories of molten brick wall exploded, pushed out and fell on the firefighters and crushed 21 firemen," said Cosgrove.
Among the dead was the fire chief, James Horan.
"It left 19 widows, 35 children orphaned, three days before Christmas, as it is today," Cosgrove, who is also a retired firefighter, told ABC7.
On Wednesday, the brotherhood and the bond among firefighters was illustrated as many worked frantically, on their knees, using bare hands, trying to reach the men who were underneath a collapsed wall.
"We leave in the morning, say, 'love ya', I'll see you tomorrow,' but some of us don't come home," said Cosgrove.
Cosgrove remembers his own childhood after losing his father who was also a Chicago fire fighter. For that reason, some of the money from sales of Chicago's Forgotten Tragedy will go to the widows and orphans fund.
In care of the firemen's Annuity and Benefit Fund
20 South Clark Street, Suite 1400
Chicago, IL 60603