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 page refers to the small American River that flows eastward from headwaters near Mount Ranier in Washington to join the Naches, Yakima, and Columbia rivers.
Although it is known to have some trout, I have not had good luck fishing here.