The sitcom "I Love Lucy," starring Lucille Ball and Desi Arnaz, was a ratings powerhouse in the 1950s, and a perpetual hit in reruns ever since. To mark the series' 70th anniversary, correspondent Jim Axelrod looks back at the making of a TV classic. He talks with granddaughter Kate Luckinbill, head of creative direction at the production company Desilu; visits the Lucy-Desi Museum and the National Comedy Center, both in Ball's hometown of Jamestown, N.Y.; and sits down with Darin Strauss, author of "The Queen of Tuesday," a novel inspired by Ball.