Sitka Mountain Ash
Sorbus scopulina Greene

Cascade mountain-ash. Collected either along the North Fork of the Salmon River from near the mouth of Hull Creek to near the junction of Hammerean Creek along the Lolo Trail in Lemhi Co., Idaho, on 2 Sep 1805, or near Hungery Creek along the Lolo Trail in Idaho Co., Idaho, on 27 Jun 1806. It is possible the three fragments on the left were found 2 Sep while the two fragments on the right were perhaps gathered on 27 Jun. The lateness of the inflorescences, however, makes it more likely all the fragments were gathered on 2 Sep. (Source)