Howell birdied seven of his first nine holes while Schniederjans birdied five of his last eight to record the lowest round of his PGA career.
"I haven't had a great start really all year on the first round," Schniederjans said. "I have had some decent first rounds and good Fridays, but this is the first really good round I've had on Thursday. It's nice to get off to a good start and hopefully keep it going."
Howell lost a playoff to Kyle Stanley in the Quicken Loans National on July 2.
"I had nine weeks off prior to the Quicken Loans with a rib injury, and it was my first injury -- knock on wood -- I've had in my career," Howell said. "I went to Quicken Loans quite honestly not prepared to play well. I had only been hitting balls for four or five days prior to that event. Expectations were extremely low and I played well."
Schniederjans also dealt with an injury recently, fighting a pulled muscle in his back since the Crowne Plaza Invitational in May.
"It kind of lingered and I tried to play through it, and then ended up taking like 15 days off without hitting a ball and still is sort of there," Schniederjans said. "Kind of have to have maintenance. ... It's been fine the last three weeks, but my game has been getting better as the days have gone on, too."
Zach Johnson, the 2012 John Deere Classic champion who hails from nearby Cedar Rapids, Iowa, was in a group of four players at 65. He hit his first 17 greens before missing on the par-4 18th hole.
"I think my irons were probably the best part of my game today truthfully,'' Johnson said. "A lot of good shots, solid shots. I got the ball in the fairway with my driver, but the irons were great."