Cover image: The colossal sculpted busts of Presidents Abraham Lincoln (shown), George Washington, Thomas Jefferson, and Theodore Roosevelt at Mount Rushmore National Memorial received their first comprehensive pure water steam cleaning in July 2005 thanks to Alfred Kärcher GmbH & Company. The German manufacturer of steam cleaning machines donated its services and worked with six National Park Service rangers and a volunteer from the nearby Crazy Horse Memorial on the project. The company has participated in 80 such cleaning projects around the world including the Brandenburg Gate in Berlin, the Colonnades of St. Peter's Square in Rome, and the Colossi of Memnon in Luxor, Egypt. Carved between 1927 and 1941 by sculptor Gutzon Borglum and a team of 400 workers, the 60-foot-tall presidential heads in the Black Hills of South Dakota are 500 feet off the ground and among the most recognizable memorials in the United States. (Courtesy of Alfred Kärcher GmbH & Company.)

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