Simpson shot an 8-under 63 at the TPC-Summerlin course Friday for a 36-hole total of 127, giving him a good start toward what would be the fourth win of his PGA Tour career.
Henry shot a career-low 60 on Thursday, but bogeyed three of the first four holes Friday and had to settle for an even-par 71.
Ryan Moore and Russell Knox were at 132.
Simpson rallied down the stretch at the Olympic Club in San Francisco to overtake and defeat Jim Furyk at the 2012 U.S. Open. His best finish during the 2013 season was a playoff loss to Graeme McDowell at Heritage Classic.
This is the second event of the tour's 2014 season. Jimmy Walker, who won the season opener last week, barely survived the cut at 3-under 139.