The Landmarks Preservation Council of Illinois (Landmarks Illinois)

Landmarks Illinois is a registered 501(c)(3) nonprofit organization dedicated to preserving and reusing significant places across Illinois. Founded in 1971, its mission is to accelerate the preservation and adaptive reuse of historic sites statewide to foster healthy, livable, and thriving communities. The organization's headquarters are located in Chicago, Illinois.

The organization provides a range of services including advocacy, technical assistance, practical resources, and educational programs to support historic preservation efforts. It offers various grant programs, such as the Preservation Heritage Fund, the Barbara C. and Thomas E. Donnelley II Preservation Fund for Illinois, and the Timuel D. Black, Jr. Grant Fund for Chicago's South Side, to provide financial assistance for preservation projects. Landmarks Illinois also holds conservation easements on historic properties to ensure their long-term protection.

In 2025, Landmarks Illinois adopted a five-year Transformational Plan (2025-2030) to guide its work, focusing on inclusive preservation, community and economic development, housing access, and climate change mitigation. Bonnie McDonald, who has served as President & CEO since 2012, is slated to step down on July 24, 2026, to accept a Loeb Fellowship at Harvard, with Frank Butterfield assuming the role of interim President & CEO. The organization continues to be active in legislative advocacy, having recently secured an extension and increase for the Illinois Historic Preservation Tax Credit through 2028.