Pomaria, traditionally placed in Hoffmannseggia or Caesalpinia, is shown to be a well-supported group of 15 species related to the Erythrostemon group of Caesalpinia sensu lato. Monophyly is well supported by analyses of both nuclear and chloroplast DNA data and by the presence of several unique morphological characters. Nine species of the genus are distributed in the arid and montane regions of the southwestern United States and adjacent Mexico, three species occur in temperate eastern South America, and three species are native to southern Africa. The genus thus exhibits both a New World amphitropical and a New World-African amphi-Atlantic distribution pattern. A biogeographical analysis suggests two dispersals within the genus account for the present distribution: one from North America to Africa and second from North America to South America.