Most gardeners are familiar with crocuses, so I don’t think I need to write up too much here.
But I’ll note that if you’re having deer / squirrel problems, you may want to try the species version, crocus tommasinianus, aka woodland crocus, affectionately known as “tommies,” which they apparently don’t like to chomp on quite as much.
Tommies are a little smaller than the cultivated species, but very adorable, and is a good choice for attempting to naturalize in lawns, since they bloom so early (the later bloomers typically get mowed too soon to be able to build up sufficient resources for reblooming).
Native gardening note: Tommies supposedly spread readily — I haven’t seen them noted as invasive in Illinois, but you may want to research further before planting them.
Lots more details and advice on planting crocus in lawns: https://oldhousegardens.com/lawncrocus
I’m not sure what varieties these are, as I planted them a long time ago! That first striped one might be “Pickwick.”