
A vote by the United States Congress to grant Puerto Ricans citizenship in 1917 set off a wave of immigration to the mainland that gained force in the 1930s and exploded in the decades after World War II.
A chief destination was Chicago, and, for decades, it had the second-largest population of Puerto Ricans beyond the U.S. territory before being supplanted by Philadelphia around 2010. The numbers have since dropped but remain close to 100,000 people, with many clustered in the Humboldt Park neighborhood.