The early 20th century was a period of dramatic change for Chicago, marked by migration, cultural growth, social challenges, and economic upheaval. During World War I and the 1920s, industrial expansion created abundant job opportunities, drawing African Americans from the Southern United States in what became known as the Great Migration. Between 1910 and 1930, the city’s African American population skyrocketed from 44,103 to 233,903, fueling the Chicago Black Renaissance, a vibrant cultural movement in music, literature, and art. However, racial tensions occasionally erupted, as seen in the Chicago race riot of 1919.

The Prohibition era (1919–1933) introduced a wave of organized crime. Notorious gangsters such as Al Capone, Dion O’Banion, Bugs Moran, and Tony Accardo battled each other and law enforcement, culminating in events like the 1929 St. Valentine’s Day Massacre, when seven members of Moran’s North Side gang were murdered. Amid this turmoil, Chicago also witnessed progressive social movements. Tenant rent strikes in 1920–1921 led to tenant protections and a heat ordinance requiring landlords to maintain a minimum winter temperature in apartments. In 1924, the city became home to America’s first homosexual-rights organization, the Society for Human Rights, which produced the country’s first LGBTQ publication, Friendship and Freedom, although it disbanded under political pressure.

The Great Depression of the 1930s dealt a severe blow to Chicago, particularly its industrial south side and riverside neighborhoods. By 1933, more than half of industrial jobs were lost, and unemployment among Black and Mexican residents exceeded 40%. The city’s Republican political machine collapsed, and Democratic mayors have governed Chicago ever since. Labor activism surged during this period, with Unemployed Councils, the Workers Alliance of America, and the Memorial Day Massacre of 1937 highlighting the struggles of workers and the unemployed.

Amid these challenges, Chicago celebrated major milestones. In 1933–1934, the city hosted the Century of Progress International Exposition, a world’s fair that showcased technological innovation and Chicago’s evolution since its founding. In 1933, Mayor Anton Cermak was fatally shot in Miami during a failed assassination attempt on President-elect Franklin D. Roosevelt, underscoring the city’s national political significance.

By the late 1930s, Chicago had become a city of contrasts: a center of cultural flourishing and industrial might, yet facing deep social and economic challenges—a dynamic that would continue shaping its identity into the mid-20th century and beyond.