Jim Thorpe? Jessie Owens? Jackie Robinson? Bo Jackson? Michael Phelps?
There's no definitive answer to the question, of course, but let's consider one other possibility: Babe Didrikson Zaharias. Over the course of her remarkable career, the Babe led her team to a national championship in basketball, won Olympic gold medals in the javelin and the 80m hurdles (as well as a silver in the high jump), won national titles in the javelin and the baseball throw, single-handedly won the national track and field championship (entering as a one-woman team, she scored more points than any other team), barnstormed as a baseball player, won a league championship as a bowler, co-founded the LPGA, and won multiple major golf championships -- including the 1954 US Women's Open, a title she captured after cancer surgery, while wearing a colostomy bag. She was a six-time winner of the Associated Press Woman Athlete of the Year, over a mind-breaking 22-year span (1932, 1945, 1946, 1947, 1950, 1954). Essentially, she was simultaneously LeBron James, Carl Lewis, Satchel Paige, and Tiger Woods.
Babe Conquers the World is an accessible yet detailed look at the life of this extraordinary athlete. It covers her many triumphs, as well as her challenges. Much like Amelia Lost from a few years ago, Babe Conquers the World doesn't shy away from its subject's faults -- Zaharias wasn't a particularly easy person to get along with, and the book notes this, while at the same time pointing out how difficult it was to be a female athlete in the first half of the twentieth century, and how hard Zaharias had to fight simply to have the opportunity to make a living.
The book is exhaustively documented and sourced; anyone who wants to follow the authors' research won't have any difficulty. It also includes a wealth of archival photographs, and though that's not of concern to the Newbery, it might be of interest to the Sibert committee.
I'm not sure it will be, as Babe Conquers the World isn't a "literary" work in the mold of something by Steve Sheinkin or Russell Freedman. Its odds of winning the Newbery, especially in what is shaping up to be a highly competitive year, are probably zero. But it's a great introduction to a fascinating figure, and I'd definitely purchase it and talk it up.
Publication in March by Calkins Creek Books