I can't guess on a purpose and don't think it has any. I don't know if they are voids and had gunk or were expansion joint material. What I will contribute to the backstory is that your slab is probably not from 1911; nor is the parging and maybe even all the concrete block depending on where you are at in IL and the level of house (brick bottom/splitface block upper, all brick replaced, etc). I might consider someone placed screed boards when they poured the slab.

We have something similar in the basement of our house, which I think was built c1945. However, ours has this continuously around the entire perimeter and connects to a ”hole” with a pipe that runs out the backyard. Ours is a poured foundation. No sump. For some reason I can’t post a photo