The large number and spectacular nature of thermal shows in the central part of the country led in the mid-1950s to the initial studies for the development of power-generating geothermal resources. By 1959 the first geothermopower plant in North America was installed in Pathe, Hidalgo, with a generating capacity of 600 KWH. Subsequently the perspective of more favorable conditions in other areas led to further investigations in Ixtlan de Los Hervores, Michoacan, and Cerro Prieto, Baja California Norte, where the largest geothermal field was discovered in 1964. Geothermoelectric generation began there in 1973, with two 37,500-MW units, and thereby the geothermal development of the country.
A census of 106 thermal spots taken from 1964 to 1965 in the central part of the country defined Los Azufres (Michoacan), La Primavera (Jalisco), and Los Humeros (Puebla) as the best geothermal prospects after Cerro Prieto. However, although some studies were done in the 1960s and early 1970s, surface exploration of Los Azufres began only in 1975 with the experience gained in Cerro Prieto, and in 1978 at Los Humeros and Larimavera. Results were favorable, and a drilling program was recommended that is presently being carried out; production has proved the presence of three major geothermal fields.