Hawthorn is a borough in Clarion County, Pennsylvania, United States. The population was 482 at the 2020 census. Hawthorn is located in southeastern Clarion County at 41°1′14″N 79°16′27″W / 41.02056°N 79.27417°W, on the north side of Redbank Creek, a westward-flowing tributary of the Allegheny River. The creek forms the boundary with A…Hawthorn is a borough in Clarion County, Pennsylvania, United States. The population was 482 at the 2020 census. Hawthorn is located in southeastern Clarion County at 41°1′14″N 79°16′27″W / 41.02056°N 79.27417°W, on the north side of Redbank Creek, a westward-flowing tributary of the Allegheny River. The creek forms the boundary with Armstrong County to the south.