Hester posted the score at the Black Creek Club, which along with The Honors Course, host the 36-hole stroke-play portion. The Honors Course will host the match-play portion of the tournament when the low-64 are established after Sunday's second round of stroke play.
Darin Newhouse is alone in second place at 5-under-par 67, which he also shot at the Black Creek Club.
David Noll, Jr. and Brian Haskell are knotted in third place at minus-4, and, like the two players above them on the leaderboard, the pair in third played Black Creek on Saturday.
Hester struggled out of the gate Saturday with a bogey at the first, but birdied four and six to make the turn at the 1 under.
He caught fire on the back side with a chip-in eagle from 40 yards out at the par-4 10th, then birdies at 12 and 13. Hester collected his second eagle on the back nine at the 14th when he pitched in from 20 yards out. He was at 7 under par for the championship, but bogeyed the 16th.
'It was okay. It wasn't lights out,' said Hester, a 35-year-old from Massachusetts.
He knows he won't post as low a score on Sunday when he plays the more difficult Honors Course.
'It's a pretty good golf course,' said Hester, who is playing in his ninth U.S. Mid-Amateur Championship. 'I'll just have to go play each hole and each shot.'
Raymond Floyd, Jr., the son of the legendary Raymond Floyd, carded the lowest round at The Honors Course on Saturday. He shot a 2-under 70 and is tied for seventh with Brian Woods.
Defending champion Austin Eaton III posted a 1-over-par 73 and is tied for 26th place.