The Liverpudlian's face lit up when she crossed the line in the 100m hurdles after seeing a time of 13.09, a lifetime best that gave her a 40-point advantage over rival Nafissatou Thiam.
The pair could not be separated in the high jump as both made it over 1.95m but could not manage another three centimetres, which would have equalled the Brit's best ever clearance.
Johnson-Thompson added her second best-ever effort of the day in the shot put, a traditional weakness for the 26-year-old, as she threw 13.86m to minimise the ground she lost to Thiam.
She could not add another PB in the 200m, coming home in 23.08, but she will still take a 96-point lead over reigning Olympic and world champion Thiam into Thursday after producing the fourth-best first day heptathlon score of all-time.
"The hurdles time has been a long time coming because I've been stuck around 13.3 for years but I never in a million years expected 13.09," Johnson-Thompson said.
"It was really important to end the day on top. To do that after not a great 200m, which hasn't been great all year... that's something to improve on next year!"
Johnson-Thompson smashed her shot put PB by 70cm
Image credit: Getty Images
Thiam meanwhile will have to out-jump Johnson-Thompson by more than a foot if she wants to level things up in the long jump but could not fault her own performances on the first day.
"Everything was good but it could have been better, in the high jump for example. [But] there was no event where I screwed it up," Thiam said.
"Everything was decent though, I'm happy and we'll see tomorrow."