Weaving through the hurried pace of dozens of office lemmings around me, trying to beat the line at Panda Express, or Taco Bell, or other quick lunchtime eats in the Thompson Center basement, I almost tripped on a loose shoelace. Bending down, I looked up, hearing the fluttering of city flags flying high above the street.

This is Chicago City Hall. Oh, the history of this place!

Legends have paced the halls inside. A few even made themselves comfy on the fifth floor. In the 1960s, the mayor of this town was known by political beat newsmen as “The Man on Five.” We’ve had colorful mayors in that office, up there—Richard J. and Richard M. are most famous. Jane Byrne, the first woman chief exec this city’s had, was a trailblazer with more than a few words for how crummy Windy City politicking can be.

Local historians will tell you, one mayor beats them all in terms of crass and color. Legends are known by simple names. In Chicago, we have one for this guy: Big Bill.

William Hale Thompsom was mayor of Chicago from 1915 to 1923, and again from 1927 to 1931. He was the last Republican to hold the office. And he’s earned notoriety as one of the most lowdown, graceless big city bosses in all of American history.

When he was first elected, he was already charging city workers $3 each month, which he pocketed to fuel his political ambitions. Yes. He was thinking of being assumed to higher power, more than the fifth floor could ever offer. He wanted the White House.

Thompson ended up not running for the mayor’s job in 1923. But on April 6, 1926, Thompson prepared himself for a comeback by debating two rats in public. He referred to the long-tailed vermin as “Doc” after mayoral hopeful Dr. John Dill Robertson, and “Fred” as in Fred Lundin, a major political powerbroker of the time.

Thompson ended up back on the fifth floor with the help of Al Capone’s organization. The April 10, 1928 election day is known by historians as the “Pineapple Primary”—named for the hand-grenades that were thrown at polling places to scare voters away.

Thompson made enemies out of Col. Robert McCormick, publisher of the Chicago Tribune, and U.S. Sen. Joseph Medill McCormick. Both newsmen saw the mayor for the crook that he was.

Several key moments in Chicago history happened while Big Bill was in charge. The 1919 race riots from July 27 to August 3 resulted in 38 deaths. Capone tried to topple Bugs Moran’s North Side Gang at the February 14, 1929 shootout at 2122 N. Clark St., in what we now know as the St. Valentine’s Day Massacre. Seven people were murdered that day.

Anton Cermak, a Bohemian immigrant, became a hero for many Chicagoans who felt disenfranchised by politicians like Thompson. When he ran for mayor, Thompson armed himself with racist comments at every chance he got.

“I won’t take a back seat to that Bohunk, Chairmock, Chermack or whatever his name is,” he said to a crowd.

Cermak was successful in wrestling control away from Thompson and won the 1931 election.

Thompson’s death on March 19, 1944 at 74 years old uncovered one more surprise for Chicago. Officials discovered safety deposit boxes with nearly $1.5 million stashed away.

Col. McCormick had the last word when Big Bill died. He published, “He has given the city an international reputation for moronic buffoonery, barbaric crime, triumphant hoodlumism, unchecked graft, and a dejected citizenship. He nearly ruined the property and completely destroyed the pride of the city. He made Chicago a byword for the collapse of American civilization.”

We might have colorful mayors of recent memory, but the Big Bill era and the rat show he presided over will never be matched.

“But then again…” I thought as I finished tying my shoelace.