Brian Guetz, who was a playoff winner at the Barton Creek Challenge earlier this year, is one shot further back at minus-5 and stands alone in second place.
Lee Williamson, the California Classic champion, heads a group of eight players at 4-under-par 68. He stands alongside Byron Smith, Chad Spencer, Trevor Dodds, Andy Doeden, Josh Habig, Marcus Jones and Jim Lemon.
Hartwick was steady over the course of his 18 holes. He was three-under par on both nines at Hazelmere Golf Club. He capped off a fine round by chipping in for birdie on the par-four 18th for the outright lead.
'I was just able to hit fairways and greens and make almost every birdie chance I had,' stated Hartwick. 'This is a great course, but you don't want to short-side yourself. You get it in that rough and it will kill you.'
Guetz, meanwhile, posted six birdies to go along with a single bogey on his day.
'It was a pretty stress-free day,' Guetz admitted. 'I just went out and did what I had to do. My game isn't flashy, nothing spectacular, but it works for me. The scorecard doesn't give this course justice. They've done a tremendous job getting it ready for us.'
Darren Griff, Joe Horowitz, Eric Jorgensen, Chris Botsford and Todd Tanner share 11th place at 3-under-par 69.
James Lepp, who became the first Canadian to win the NCAA Individual Championship in 2005, made his professional debut today in his home province. He carded a 1-under-par 71 and stands in a tie for 25th.
Ryan Miller won this crown two years ago the last time the event was held. He opened with an even-par 72 and is part of a logjam tied for 48th.