The last to die was officer Terrence Knox, killed in 2011.
Also honored were officers Sidney Sam, William Goles and Cornelius Rourke.
And the first of the group to die was officer John Furlong, who was killed almost a century ago, but not before he was able to leave a clue about who had attacked him.
"He told the nurses he'd been jumped by four gangsters," said Phil Cline, former Chicago Police superintendent. "He then lapsed into a coma and two days later on October 27, 1915, he died.
That information helped investigators find Furlong's killers who were arrested and convicted.
