It's a utility location service that marks their presence prior to excavation. In MO it's called 1-800-Dig-Rite. Believe 811 may be in Illinois.
I read that 811 works in MO. https://811beforeyoudig.com/811-states/state-missouri/ Check all about it here: https://811beforeyoudig.com/for-homeowners/
Probably. Gotta remember: I've been out of the loop for almost 10 years now. Seemed like states were standardizing this back in the day, and I wondered why Missouri was still an odd duck. Apparently they figured it out finally.
Edit: If you search "Digrite", it takes you to MO's 811. And I was wrong: Illinois calls there's J.U.L.I.E. So yeah, I'm a dinosaur...
If you look at the dig site and the 800 number its dig rite.
But 811 has been a thing for some time.
Ah, ok. I guess The United Emirates of Ohio also uses 811 for the utility marking service. TIL.