Successive rounds of 65 meant Kaymer had equalled the lowest halfway total in Major championship history (130), as well as eclipsing the US Open record of 131 set by Rory McIlroy at Congressional in 2011.
The 29-year-old's six-shot half-way lead also matched the championship record shared by Tiger Woods (2000) and McIlroy (2011), but some fiendish pin positions meant only two of the 67 players to make the cut broke par on yesterday.
Rickie Fowler and Erik Compton carded matching rounds of 67 to finish three under par, while Sweden's Henrik Stenson bogeyed the 18th to lie two under alongside Dustin Johnson, both players shooting 70.
Kaymer finished eight under par after three-putting four times in a round of 72 that could have been much worse if not for a stunning eagle on the fifth and a birdie from six feet on the last.
Compton is playing in just his second Major championship at the age of 34, but even more remarkable is the fact that he has undergone two heart transplants. He took up golf after the first one when he was 12 and, after suffering a heart attack in 2007, drove himself to the hospital. He had his second heart transplant six months later.
"I felt comfortable today and even when things weren't going well, I wasn't getting over anxious," Compton said. "But it is a Major and I know you guys [the media] put a lot of emphasis on people who don't have experience.
"But I've been playing good golf for a long time, since I was a junior golfer, college golfer, and playing at other pro levels. And this year I've had a great year. We're playing against the same guys and I just try to hit fairways and greens. It shouldn't feel any different than any other tournament.
"I have been through a lot in my life and some were a lot more adrenaline pressure situations than hitting a tee shot on 18. Putting things in perspective may help me."
Fowler began the week by paying tribute to the late Payne Stewart, wearing his idol's trademark plus fours for the opening round on Thursday.
Stewart won his third Major title in the 1999 US Open at Pinehurst, but died just a few months later at the age of 42 when the private plane in which he was travelling depressurised and eventually crashed in a field in South Dakota.
"It was awesome to be able to come out here and wear the plus fours in honour of Payne," Fowler said after a round containing five birdies and two bogeys. "It was very special. I sent a message to Chelsea Stewart [Payne's daughter] afterwards and said, 'I hope you guys liked it as much as I did', because it was a lot of fun walking around with her dad. It was definitely special."
No rain had fallen overnight to soften the greens and the pin positions tucked close to the edge of almost every green prompted veteran American Kenny Perry to say after his 74: "I tell you what - it was a golf course of 18 of the toughest pins I've ever seen. It was probably the hardest set-up I've ever experienced in a Major championship."
Those sentiments were borne out by some of the early completed scores which saw Boo Weekley shoot 80, Russell Henley 82 and Japan's Toru Taniguchi an 18-over-par 88 which contained six pars, seven bogeys, four double bogeys and a triple bogey.
Defending champion Justin Rose was joint 10th after a round of 70, but the 33-year-old was left frustrated by a number of errors which damaged his bid to become the first back-to-back winner since Curtis Strange in 1989.