The second major of the PGA Tour season tees off this morning with first-round play at the U.S. Open.  The tournament returns to The Olympic Club in San Francisco for the first time since 1998 and the fifth time overall.  A pair of star-studded groupings will take the spotlight for the first two rounds.  Defending U.S. Open champion Rory McIlroy, and fellow top-ranked players Luke Donald and Lee Westwood are in one group.  Four-time U.S. Open winner and 14-time major champion Tiger Woods, five-time U.S. Open runner-up Phil Mickelson and reigning Masters champion Bubba Watson are in another.  The Olympic Club is one of the oldest venues in the country, established in 1860.