This would have been at a time when it was nothing but native plants. Which means it would have been teeming and crawling with native insects (note that native plants will support more insect life than non-native ones - because the non-native insects that evolved to live off the non-native plants, are missing).
So it would have been noisy with insect life.
Butterflies. Creepy crawlies. Spiders. Dragonflies. Gnats. And things I'd have a hard time finding a common name for, moving around.
And then the native reptiles and snakes that eat them (remember, present at a higher density then because there was more of the food they like, and fewer people).
And the birds that feed off them, also present in higher numbers because there were no humans, no domestic cats, and no habitat loss restricting their numbers. No non-native predators at all.
Zero percent pesticides compared to what we have now, much more water (nothing having been dammed or redirected), no farming depleting nutrients in the soil, only 100% virgin high quality composted soil. And so forth.
It would make considerable noise, all the additional living biomass all these ecosystem positive changes would support.
It's pretty easy to confirm this yourself, if you go to a small nature preserve that's been restored with native plants during the summer, and just sit there and observe for 10-20 minutes. And that's only a weak imitation of the amount of biomass those prairies would've supported.