Defending champion Jim Thorpe, who fired a 60 in the second round last year, is alone in third place at 5-under-par 65. Mike Hill is in fifth at minus-4 at the Red Course at Eisenhower Park.
Jacobsen, who is competing for the first time since hip surgery, broke into red figures at the par-5 third. He two-putted from 20 feet for birdie, then holed a 20-footer for birdie at the par-3 fifth.
Jacobsen, who won in Hartford last year on the PGA Tour, collected back-to-back birdies at seven and eight. He had a 6-footer for birdie at the ninth but missed the putt to make the turn at 4-under 31.
The 50-year-old knocked a sand-wedge to 15 feet for birdie at the 11th and made it two in a row with a 20-footer at the 12th. Jacobsen's 3-iron tee shot at the par-3 13th buried in a bunker and he made bogey to fall one back. He atoned for the mistake with a 15-foot birdie putt at No. 15 to grab a piece of first.
'I played well,' said Jacobsen, who also shared the first-round lead at his only other event, the SBC Classic, where he took third. 'I drove the ball well and putted well.'
Pate, who won the U.S. Open in 1976, used spectacular iron play to get his share of the lead. His four birdie putts on the front nine were all from inside 10 feet but the flat stick went cold on the back side.
He made a 15-footer for birdie at the 10th but missed a 6-footer for birdie at 11 and a 10-foot birdie try at No. 13. Pate made a clutch par save from 6 feet at the 15th before hitting a 5-iron to 6 feet to set up birdie at the last.
Pate's 6-under-par 64 was his lowest round on the Champions Tour and his lowest numerical score in competition since the third round of the 1982 Phoenix Open.
'It's been 22 years since I've last been in contention in a golf tournament,' said Pate, who has not owned a share of the first-round lead in a tournament since the 1980 event at Southwind. 'I'm putting well and could have shot 60 today.'
Wadkins, who claimed this title in 2001, birdied three in a row from the third but a poor drive at the seventh resulted in a bogey. He reclaimed the lost stroke with a tap-in birdie at the ninth.
Wadkins made it three in a row with short birdie putts at 10 and 11 and reached 6 under for the tournament with a 10-foot birdie putt at the par-4 14th.
He found trouble at the 15th when his approach shot plugged in a bunker. He could not save par and fell one off the pace. Wadkins then sank a 15-foot birdie putt at the 17th to join Jacobsen and Pate in first.
'There are some birdies out there, but you've got to keep it in the fairway,' said Wadkins, who battled back problems all of last year. 'I don't think you'll see anyone do what Thorpe did last year.'
Wayne Levi, Bob Gilder, Tom Jenkins, Vicente Fernandez and Dave Stockton are tied for sixth place at 3-under-par 67.