The 119th edition of the Penn Relays, the oldest and largest U.S. track and field event, will commence today at the University of Pennsylvania’s Franklin Field and run through Saturday. More athletes have participated in the Penn Relays than any other single meet in the world, and it's the most watched globally following the Olympics and world championships. It will feature more than 18,000 competitors at the middle school, high school, college and Olympic levels from over 450 schools and two dozen countries. Due to the sheer volume of competition, there will be one event every five minutes over the 33 hours of activity. The must-see event is a relay series -- USA vs. The World -- in which the Americans are defending their 2012 sweep of six relays.