It is said that a picture is worth a thousand words, but in the case of National Geographic, the magazine could very well survive on photographs alone. After a century of publishing visually stunning and telling portraits, National Geographic and the Smithsonian's National Museum of Natural History have created IN FOCUS: NATIONAL GEOGRAPHIC GREATEST PORTRAITS. The photos include some of the magazine's best-known and most relevant shots. Through April 18. Free-$7.50. Mon.-Sat., 9:30 a.m.-5 p.m. The Southern Museum of Civil War and Locomotive History, 2829 Cherokee St., Kennesaw. 770-427-2117. www.southernmuseum.org.