New regional distribution records and range extensions involving one Canadian province, 17 Mexican states, 10 USA states, and five Central American countries are given for 53 species of Ephemeroptera. In Mexico, states with the greatest number of new species records include Queretaro, Mexico, Nueva Leon and Tamaulipas. For the USA, states with the greatest number of new species records include Oklahoma, Wisconsin, Kentucky and Texas. Farrodes flavipennis, Lachlania fusca and Leptohyphes peterseni records are the first for Mexico and North America, and the presence of Tricoryhyphes mulaiki in Texas represents a new USA record. New Central American country records include Americabaetis pleturus in El Salvador, Camelobaetidius arriaga and Thraulodes zonalis in Guatemala, Euthyplocia hecuba in Honduras, and Thraulodes pacaya in Costa Rica. Highly disjunct northern range extensions discovered for Tricorythodes robacki and T. albilineatus in the St. Croix River on the Minnesota/Wisconsin border parallel a pattern seen in some other psammophilous mayflies in eastern North America. Far eastern Oklahoma records of Acentrella nadineae, Caenis macafferti, and Eurylophella prudentalis demonstrate a common relationship between the Central Highlands and the Southern Appalachians.