The Illinois Department of Public Health (IDPH) announced that the largest measles outbreak to affect the state of Illinois since 1990 is officially contained as no new cases have been reported for more than 42 days, two full incubation periods. A total of 67 measles cases were reported during the outbreak, which started March 7, with the vast majority linked to a Chicago shelter for new arrivals. Cases eventually extended beyond Chicago to suburban Cook County, DuPage, Lake and Will counties, but were rapidly contained in all these other locations. Throughout the outbreak, IDPH, the Illinois Department of Human Services (DHS), and Illinois Emergency Management Agency (IEMA) mobilized resources to support local public health partners, starting with the Chicago Department of Public Health (CDPH). The state also provided epidemiological support for county public health departments for Cook, DuPage, Lake and Will counties. Early in the outbreak, IDPH activated Emerging Diseases funding to support a DHS-run quarantine hotel-shelter in Chicago that allowed for the most vulnerable new arrivals (pregnant and immunocompromised people and young children) to quarantine safely while also helping decompress the shelter with the largest outbreak.