Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
Beware: There were a lot more footsteps before us than we may realize. Most high mountain lakes and upper tribs never had fish in them of any kind, until people started hauling them up in buckets, and not keeping records, and later by airdrop. There are precious few (if any) places left that fish aficionado's (of many ilks) haven't messed with things. We can consider nature's order pretty much "messed with" across the board.