The massacre represented the high-water mark of Capone’s power. The Depression hit Chicago hard. Big Bill (“The Builder”) Thompson had plunged the city into debt and would soon be turned out of office a second time. A sobered citizenry was less inclined to tolerate high-living gangsters and their political cronies. Capone was booed when he showed up to watch a Northwestern football game in the northern suburb of Evanston.

Beginning in 1930, the Capone story moved rapidly toward its familiar anticlimax. The Treasury Department assigned the intrepid Frank J. Wilson, an agent in its Special Intelligence Unit, to put together a tax-evasion case against Capone. Given the fact that Al owned no property in his own name and avoided banks, checks, and receipts, Wilson’s job wasn’t easy. One of the unit’s important informants was Edward J. O’Hare, a lawyer whose control of the patent on the mechanical rabbit used at dog tracks led him into partnerships with gangsters, including Capone. In 1939 unknown assailants shotgunned O’Hare to death in reprisal. He never lived to take pride in the gallantry of his son, World War II ace Butch O’Hare, for whom Chicago named its international airport.

We can’t ignore Elliott Ness, whose headquarters were at 600 South Dearborn, on the southern edge of the Loop. His third-floor office looked out on Harrison Street. Ness elbowed his way into history with a book, a television series, and several movies, all of them posthumous. It’s a telling comment about the times that Ness’s simple failure to accept bribes qualified him for hero status.

The rationale for the “Untouchables” can actually be traced back to 1917. One of the compromises that steered the Eighteenth Amendment through Congress was a concession removing Prohibition agents from the ranks of the civil service. The political appointees who marched out to enforce the unpopular law were paid a top salary of twenty-three hundred dollars, less than a garbage collector. They were quickly corrupted.

Ness, a University of Chicago graduate, and his group of handpicked agents did ax their share of beer barrels. He did arrange for a parade of confiscated booze wagons past the Lexington, sending Capone into a tantrum. But Ness’s small crew was trying to empty an ocean of beer with a teacup. During the first half of 1930 he cost the outfit a million dollars, less than 4 percent of what the bootleggers were handing out in bribes alone.

By the time Ness swung into action, Capone had already predicted the end of Prohibition. He was diversifying. Labor and business racketeering were just coming into criminal vogue. Corrupt unions and associations like the Electric Sign Club extorted money from businesses under the threat of strike or violence. Capone himself came to control many of Chicago’s hundreds of rackets, including associations for Soda Pop Peddlers, Motion Picture Operators, and Jewish Chicken Killers.

In a real sense Capone and his mentor Torrio can claim to