A sign directs visitors to the Mark Twain family plot in Woodlawn Cemetery in Elmira, N.Y. David Duprey/AP hide caption

itoggle caption David Duprey/AP
Courtesy of Scholastic

Author Dan Buettner has traveled the globe visiting "blue zones," where people tend to live longer and lead healthier lives. Cheryl Tiegs/National Geographic Books hide caption

itoggle caption Cheryl Tiegs/National Geographic Books

The legacy of U.S. Supreme Court Justice William J. Brennan Jr., shown on April 20, 1972, is spelled out in more than 1,300 legal opinions. John Rous/AP hide caption

itoggle caption John Rous/AP