(Brookline, MA) -- One of golf's toughest majors is back. The first round of the US Open at The Country Club in Brookline tees off this morning. Jon Rahm is the defending champion after winning last year's tournament with a finish of six under par. Rahm will be joined by Collin Morikawa and James Piot for the opening round. Erik Barnes, Michael Thorbjornsen, and Matt McCarty will be among the first group of players teeing off the first round.