Final answer:
Al Capone built his crime empire during Prohibition, mainly from bootlegging, alongside other criminal activities. He earned over $100 million annually from these operations, and his downfall came from tax evasion.
Step-by-step explanation:
Al Capone was able to build a crime empire primarily through Prohibition-era bootlegging. The Prohibition sparked a significant rise in organized crime, and Capone's operations in Chicago, often referred to as the Chicago Outfit or Chicago mafia, were a prime example. By 1927, his organization was involved in a variety of illegal activities, including bootlegging, prostitution, gambling, loan sharking, and murder, earning him more than $100 million annually. Capone's success was largely due to his effective organizational structure and the ability to bribe local police, which allowed his operation to flourish. Despite the array of criminal activities, it was tax evasion that eventually led to Capone's imprisonment, illustrating the difficulty authorities faced in pinning down his illicit operations directly.