Good news for architecture buffs and Frank Lloyd Wright fans: One of Wright’s greatest buildings, the S.C. Johnson Research Tower in Racine, Wis., will open for the first time to public tours May 2.

Listed on the National Register of Historic Places, the 15-story tower is revered for its treelike internal structure, which is anchored by a “taproot” foundation sunk deep into the ground. The building’s concrete core supports alternating square and round floors. Curving bands of brick and Pyrex tubing give the tower a streamlined look reminiscent of Depression-era art moderne designs.

Though the building often appears in architectural history books, it has been off limits to the public. Until now.

 The tours, which will be free, will run through Sept. 27. Future tours are planned but no specifics were announced.

 Completed in 1950, the Research Tower was where S.C. Johnson’s research and development scientists developed such familiar products as Raid, Glade, OFF! and Pledge.

"Frank Lloyd Wright’s creative vision and iconic architecture have served as a source of inspiration for our business for more than 75 years,” Kelly Semrau, an S.C. Johnson senior vice president, said in a statement. “There is no place that demonstrates this more than the Research Tower."

The tower closed in 1982 when the company moved its researchers to a nearby building, saying that the upgrades required to bring the tower up to modern safety standards would have destroyed Wright's vision.

Inside the building, which has undergone a yearlong restoration, exhibits on two floors will tell the story of how Wright’s architecture stimulated S.C. Johnson scientists. The exhibits will also include archival photographs and correspondence between Wright and company leader H.F. Johnson, Jr.

 The tour, which will last two hours, will bring visitors inside several buildings on the S.C. Johnson campus, including the tower and the Wright-designed Administration Building, a low-slung office building that opened in 1939 and is best known for its lily pad-shaped interior columns.

 Plans call for the tours to be held on Fridays and Saturdays. Starting March 24, reservations can be made online at scjohnson.com/visit, or call 262-260-2154.

bkamin@tribune.com

Twitter @BlairKamin