The North American genus Ceratagallia Kirkaldy, 1907 is redefined to include subgenus Aceratagallia Kirkaldy, 1907 (= Ionia Ball, 1933, syn.nov.) with 78 species in two subgenera. Two additional new species are unplaced to subgenus: C. acerata from Oregon, and C. emarginata from Mexico. The typical subgenus Ceratagallia has 30 species, including C. gillettei (Osborn & Ball, comb.nov.), C. sordida (Oman, comb.nov.), and two new species C. ana from Mexico and C. vipera from Washington state. Subgenus Aceratagallia has 46 species, all new combinations under Ceratagallia. The economic "species" formerly known as "sanguinolenta" is divided into the Canadian clover leafhopper C. humilis (Oman) and the American clover leafhopper C. agricola sp.nov. Other new taxa in subgenus Aceratagallia include 18 new species and seven new subspecies: alaskana (ssp. of siccifolia) from Alaska; omani on the Pacific coast from Oregon to British Columbia; clino and lophia from the Oregon interior; compressa (ssp. of siccifolia), gallus, modesta, okanagana, and zacki (ssp. of nanella) from intermontane valleys of the Pacific northwest and southwestern mountains; interior (ssp. of humilis) and rossi from the Sonoran subregion; australis (ssp. of nanella), coma, ebena, entoma, falcata, oionus, and venosa from Mexico and Texas; alvarana (ssp. of humilis), cerea, cristula, harrisi, semiarida, and viator widespread between the Appalachian and Rocky Mountains; and whitcombi (ssp. of robusta) from Florida to Arizona. Four former species are reduced to subspecies: compacta Oman and poudris Oman in C. robusta (Oman), helveola Oman in C. cinerea (Osborn & Ball), and truncata Oman in C. humilis. The taxa are keyed and illustrated, and their phylogeny is discussed.