With the onset of Prohibition, Kid Cann and his brothers were transformed from small time hoods into major figures in the American Mafia. His ties to the Chicago Outfit and New York’s Genovese crime family date back to the Prohibition period. According to a later trial, they would legally import industrial grade alcohol from Canada, ostensibly for their perfume factory, and divert it to their illegal distilleries in the forests near Fort Snelling. Also, according to the book Minnesota 13, Kid Cann and his brothers made frequent trips to Stearns County, Minnesota to purchase the area’s legendary moonshine from local farmers. Some was disposed of in the Twin Cities, but most of it was sold to the Chicago Outfit, which was then bossed by Al Capone. The same book also alleges that the Blumenfelds owned a lakeside cabin near Melrose, Minnesota. By his 20’s, Blumenfeld and his brothers, Harry Bloom and Yiddy Bloom (their family name had been changed by this time), held considerable power over the Jewish neighborhoods in North Minneapolis and oversaw illegal activities such as bootlegging, prostitution, and labor racketeering. According to Twin Cities crime reporter Paul Maccabee, Kid Cann’s rivalry with Minneapolis’s Irish Mob ended after he and Irish Mob boss Tommy Banks divided their territories with a handshake.

A number of deaths are attributed to Blumenfeld and his gang, including journalists who were killed after writing articles exposing the inner workings of his organization as well as his ties to corrupt politicians from several parties. A Jewish restaurant owner who recalls this era once said that the Blumenfelds were worshipped by several generations of neighborhood boys. There was a high degree of political and civil corruption in the region in the 1920s and 1930s. The mainstream newspapers hardly mentioned what was going on, as any outlet that published articles critical of the status quo was threatened. Some small tabloid newspapers attempted to report what was going on, but reporters and editors quickly became targets. Howard Guilford of the Twin City Reporter was shot and killed on September 6, 1934. A decade later the paper lost another reporter when Arthur Kasherman was killed on January 22, 1945. The most notorious murder was that of Walter Liggett, the founder and editor of a weekly paper called The Midwest American. He had been threatened and offered bribes to stay quiet, but he persisted in reporting on links he found between organized crime figures and Minnesota’s ruling Farmer-Labor Party. Liggett was beaten up, prosecuted for a non-existent rape incident, and finally died after being machine gunned in the alley behind his home on December 9, 1935. His wife and daughter witnessed the assassination as did several neighbors. All identified Kid Cann as the shooter. Kid Cann was indicted by a grand jury, but poor investigative work and a careless trial meant that he was acquitted.[citation needed] Liggett’s widow would always believe that Minnesota Governor Floyd Olson was deeply implicated in the murder. Her husband had repeatedly accused the governor of corruption.

Blumenfeld was indicted for the killing of taxicab driver Charles Goldberg, and was also suspected of being responsible for the attempted murder of police officer James H. Trepanier at the Cotton Club in Minneapolis. Paul Maccabbee, however, writes that Kid Cann, while present, had no part of the shooting, which was likely committed by fugitive bank robber Verne Miller. As the area streetcar system, operated by Twin City Rapid Transit, was being dismantled in the early 1950s and replaced with diesel buses, Blumenfeld owned a 16% stake in the company. He was accused of allying himself with a corporate raider, using force to intimidate stockholders, and disposing of the scrap metal on the black market after their hostile takeover had succeeded. Some historians believe he held considerable responsibility for what happened, but when a federal court case years later led several executives from the company to go to prison, Blumenfeld was not convicted. What remained of Twin City Rapid Transit was taken over at the behest of Governor Orville Freeman by noted Minneapolitan Carl Pohlad in 1960.

In 1959, he was convicted on federal charges of transporting a Chicago prostitute named Virginia Tollefson across state lines (see Mann Act). Although this conviction was later overturned on appeal, he was again tried and convicted of jury tampering and extorting kickbacks from bars and nightclubs throughout Minneapolis. The extortion was carried out by threatening to deny them liquor licenses. During the sentencing phase of this trial, it was revealed that Kid Cann was receiving a cut of the money skimmed from at least one Las Vegas casino. After his release from prison, he moved to Miami Beach, Florida with his friend Meyer Lansky. They reportedly continued to make money through illegal activities, though they changed tack, focusing instead on stock market fraud, money laundering, and questionable real estate dealings. He frequently visited his family and friends in Minnesota and declared to a Minneapolis reporter in 1976 that he had recently turned down an offer to write his memoirs. He said, “I have nothing to say, really.” He died in Minneapolis’ Mt. Sinai Hospital of heart disease in the summer of 1981. Rabbi Max Shapiro of Temple Israel recited the graveside services when Kid Cann was interred at the Adath Yeshurun Cemetery in Edina, Minnesota.