From public corruption to terrorism, Fitzgerald has overseen many high-profile cases during his nearly 11 years on the job.
Fitzgerald, then 40 years old, arrived in Chicago with a reputation as an unrelenting assistant U.S. Attorney in New York. He prosecuted terrorists who bombed the World Trade Center in New York and overseas U.S. Embassies in Kenya and Tanzania. His appointment was urged by former U.S. Senator Peter Fitzgerald, not related, who thought public corruption in the Northern District of Illinois was out of control.
"Pat Fitzgerald is the best person to serve as U.S. Attorney for the Northern District of Illinois," said Sen. Peter Fitzgerald, (R) Illinois, in 2001.
"There was a sense that things were cozy during the period of time prior to him coming here ... and I think there was this element with regard to Pat which was, what's he going to do about it," said Anton Valukas, former U.S. Attorney from 1985-1990.
A month after his appointment, Fitzgerald pulled the trigger on a pending corruption case against Cicero president Betty Loren Maltese.
A few months later, Operation Safe Roads was charged. Its indictments included, among others, former Republican governor George Ryan.
Other cases charged dozens of city officials and contractors in the hired truck scandal, including top officials in Mayor Richard M. Daley's administration.
Fitzgerald's reputation as a bipartisan corruption buster was well-established in late 2008 when he ordered FBI agents to arrest Ryan's successor, Democratic governor Rod Blagojevich.
"The conduct would make Lincoln roll over in his grave," Fitzgerald said after Blagojevich's indictment.
" People are going to look at these years and say he prosecuted these type of cases without regard to party affiliation. The next U.S. Attorney, whoever he or she is going to be, is going to be expected to maintain that standard," said Valukas.
Suspects have publicly questioned alleged strong arm tactics used by Fitzgerald's investigators.
"He has caused three depths with these Gestapo type tactics," Cook County Commisioner William Beavers, who was indicted on charges he pocketed campaign funds without paying federal taxes.
Valukas, now in private practice, says Fitzgerald would be a top candidate to lead the FBI. He theorized a temporary U.S. Attorney would be appointed to the Northern District until the presidential election is decided.
"My guess is its more likely there will be an interim U.S. Attorney pending the election," said Valukas.
On another front, Fitzgerald dealt organized crime a severe blow with the Family Secret investigation that charged leading Outfit members with 18 unsolved murders.
Fitzgerald married and fathered two children during his time in Chicago.