Korir claimed his first major marathon victory, finishing ahead of Ethiopia's Mohamed Esa (2:04:39) and another Kenyan, Amos Kipruto (2:04:50).
Korir was part of a seven-man group at the head of the course 30 kilometres in before he hit the accelerator and shed his rivals.
Four of the top five were Kenyans, with Vincent Ngetich and Daniel Ebenyo finishing off the podium.
"It was really nice to run my PB and win in Chicago," said Korir, adding that he used Kiptum's world record run at the same event last year as a source of motivation.
"Today I was thinking about Kiptum and I said 'last year if he could run under 2:01, why not me?' So I had to believe in myself and try to do my best."
Kiptum set the world record in 2:00:35 in Chicago in October 2023 but died at the age of 24 just four months later in a car accident in his native Kenya.