Twain's boyhood home in Hannibal, pictured circa 1955, is now a museum. Three Lions/Getty Images hide caption

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After John F. Herring by Ken Perenyi, circa 1989. Courtesy of Pegasus Books hide caption

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MASS MoCA is a complex of 26 renovated 19th-century factory buildings. The site was formerly the home of Arnold Print Works (1860-1942) and Sprague Electric Company (1942-1985). MASS MoCA hide caption

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Edward Hopper's wife, Josephine N. Hopper, served as his model for 1952's Morning Sun. Columbus Museum of Art/Howald Fund hide caption

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Tilman, Arlington National Cemetery, Arlington, Virginia, 2012 Charlotte Dumas/Courtesy of the Corcoran Gallery of Art hide caption

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Experts say glass buildings kill millions of birds every year. Scientists at Powdermill Avian Research Center are studying ways to help prevent this. Here, a volunteer tags a black hooded warbler in Rector, Pa., in May. Maggie Starbard/NPR hide caption

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Architect Guy Maxwell holds a printout of his proposed design for the new Bridge Building at Vassar College in Poughkeepsie, N.Y. John W. Poole/NPR hide caption

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