Mystery Castle was constructed circa 1934-1945 by Boyce Luther Gulley, who built the complex by hand for his daughter Mary Lou without plans, permits, or formal architectural or engineering training. Gulley melded organic architecture and folk art, inspired by local materials in the Sonoran Desert and Indigenous cultures of the American Southwest and Mexico, and incorporated recycled or rejected objects to build an 18-room multi-story structure that has survived in the harsh Arizona desert climate for almost a century. After Gulley’s death in 1945, Mary Lou and her mother, Frances, dedicated their lives to maintaining, operating, promoting, and preserving Mystery Castle as their home and a nationally known tourist attraction featured in LIFE magazine.

Before Mary Lou died in 2010, she created a small local foundation entrusted with preserving Mystery Castle, but vandalism and multiple break-ins caused extensive damage, and the foundation now does not have the resources to maintain or operate the property, which is also under threat of increasingly encroaching suburban development. Lacking other options for protecting or operating the property and hoping to engage potential partners to find a solution, the foundation applied for a demolition permit after consultation with the City of Phoenix Historic Preservation Office.

As expected, the City of Phoenix denied the permit, resulting in a one year stay of demolition to provide time for advocates to explore preservation alternatives. The Phoenix Historic Preservation Office hired a consultant to conduct a conditions assessment with recommendations for stabilization and public accessibility upgrades. Preserve Phoenix and a new “Friends of Mystery Castle” group are leading a grassroots effort to save the building, but additional partners and supporters will be needed to prevent demolition and ensure a publicly accessible reuse for this unique art environment.

Mystery Castle was named to the National Trust's 11 Most Endangered Historic Places list for 2025.