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.
This one was surprisingly straightforward to identify. The lack of a sclerite at the base of the lateral hump narrows the field quite a bit, and the other options followed fairly obvious characteristics to Clostoeca, which only has one species, Clostoeca disjuncta.
Described by Needham, J.G. & Claassen, P.W. (1925) A Monograph of the Plecoptera or Stoneflies of America North of Mexico. The Thomas Say Foundation II, 1–397.