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.
Size 11 mm. Prior to this photo the specimen dropped its large egg mass that was a very dark (almost black) olive sphere almost twice the diameter of the abdomen. Notice the abdomen visible through the wings is both thickened and shortened post egg drop.