The oldest exposed rock in the world is in Canada's Northwest Territory. It's called the Acasta Gneiss. It has been dated around 4 Billion years old.
https://en.wikipedia.org/wiki/Acasta_Gneiss
The second oldest is the Kawana Peninsula in Upper Michigan. Dated over 1 billion years old.
https://www.nps.gov/kewe/learn/natur...c-timeline.htm