The nomination was rejected because the organization wanted to see a larger nomination with more Wright properties. In 2008, the National Park Service submitted the Taliesin estate along with nine other Frank Lloyd Wright properties to a tentative list for World Heritage Status, which the National Park Service says is "a necessary first step in the process of nominating a site to the World Heritage List." After revised proposals, Taliesin and seven other properties were inscribed on the World Heritage List under the title "The 20th-Century Architecture of Frank Lloyd Wright" in July 2019. In 1987, the National Park Service evaluated the 1,811 NHLs nationwide for historical integrity and threat of damage. Taliesin was declared a "Priority 1" NHL, a site that is "seriously damaged or imminently with such damage." Furthermore, the site was listed by the National Trust for Historic Preservation as one of America's Most Endangered Places in 1994, citing its "water damage, erosion, foundation settlement and wood decay." Taliesin Preservation, Inc. (TPI), a non-profit organization, was established in 1991 to restore Taliesin. Rehabilitation On June 18, 1998, a severe storm damaged the estate. The large oak tree at the center of the tea circle in the courtyard fell down on top of the house. Ten days after this, heavy rains caused a mudslide north of the building. The next year, another storm collapsed a tunnel underneath the studio wing. A 1999 grant from Save America's Treasures helped defray costs to re-roof Taliesin III, to stabilize its foundation, and to connect it to a local sewage treatment plant. Over $11 million has been spent on the rehabilitation of Taliesin since 1998. Unfortunately, its preservation is "fraught with epic difficulties", because Wright never thought of it as a series of buildings with a long-term future. It was built by inexperienced students, without solid foundations. Financing renovations has been challenging because revenue from Taliesin visitation has been lower than projected. TPI provides tours from May 1 through October 31. Other visitation opportunities are available the rest of the year, but these are variable and visitors are encouraged to visit the organization's website. Roughly 25,000 people visit Taliesin each year. Assessment Architectural historian James F. O'Gorman compares Taliesin to Thomas Jefferson's Monticello, calling it "not a mere building but an entire environment in which man, architecture and nature form a harmonious whole." He continues that the building is an expression of