A key is given for 4 subgenera in the aphid genus Uroleucon Mordvilko in America north of Mexico. An annotated list and keys are presented for 44 species of the subgenus Uroleucon, 12 species of the subgenus Uromelan Mordvilko, and 1 species of the subgenus Satula Olive. Nine new species are described in the subgenus Uroleucon: Uroleucon (Uroleucon) alaskense n. sp., U.(U.) arnesense n. sp., U.(U.) boreale n. sp., U.(U.) chani n. sp., U.(U.) deltense n. sp., U.(U.) elephantopicola n. sp., U.(U.) ivae n. sp., U.(U.) maximilianicola n. sp., and U.(U.) vancouverense n. sp. Two subspecies, U. (Uromelan) illini subspecies crudae and sangamonense, are listed here merely as color forms of illini (Hottes and Frison), not subspecies. Uroleucon (Uroleucon) muralis Buckton, U. (Uromelan) compositae (Theobald), and U.(U.) solidaginis (Fabricius) have been listed as present in North America, but there appear to be no authentic records of their occurrence. Uroleucon (Uroleucon) pseudochrysanthemi (Olive) is declared to be a synonym of U.(U.) lanceolatum Patch, and U. (Uromelan) squarrosum (Sanborn) as a nomen dubium.