Ben Martin's first-round fireworks in New Orleans gave him a two-stroke lead as he shot the course record in Avondale, while Justin Rose and Ernie Els lie well off the pace.
On a blustery day in the southern state of Louisiana, Martin went out in a six-under 30 before coming back in 32 for a stunning round of 10 under that included no bogeys.
Rose, though, could only muster a 71 as his iron play dipped below the standard set by the world number 11 - and Paul Casey is just one shot better off at minus two.
Ernie Els shot level par to lie 10 strokes back, but Swede Peter Hanson is right in contention heading into Friday's second round after his 65 left him at seven under and just three back.
American Andrew Svoboda lies in second all by himself after he matched the previous course record of 64 before Martin moved past him late on, while South Korean prodigy Seung-yul Noh matched Hanson's 65 to sit third after day one.
Leader Martin is in indifferent form, to say the very least, having missed seven of his last nine cuts on the PGA Tour but in between he's finished third both times - including at Hilton Head last week during the RBC Heritage.
After his storming front nine saw him record back-to-back birdies on three occasions, there were mutterings of a Tour 59 and that gathered pace at 10 and 11 as he again made gains.
A birdie three at 13 left him nine under and needing to go four under through his last five holes to complete the first-ever 59 recorded on the American tour. Sadly, three pars followed but his day was completed in style when he holed a chip on the par-three 17th, before parring the last to ensure a plaque with his name would be on the Course Record board.
It was also his best-ever round on the PGA Tour, beating his previous best by three shots.
He said afterwards: "It was one of those days you dream about. I started the round with two birdies in a row and they just kept rolling in.
"Really, everything was working well," Martin added. "It was just one of those days, just like you draw it up."
There's good and bad news for the South Carolina native.
Firstly, Martin will have to buck a trend starting to develop over the Atlantic, with only four of the previous 22 first-round leaders going on to win the tournament. However, in New Orleans, six of the last nine victors have been first-time winners.
In golf, the only thing certain is that Martin will at least belong to one of those stats come Sunday night.
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