Mon Rivera Born May 25, 1925 Mayagüez, Puerto Rico Died March 12, 1978 Manhattan, New York Occupation musician Mon Rivera is the common name given to two distinct Puerto Rican musicians (both born in Mayagüez), namely Monserrate Rivera Alers (originally nicknamed Rate, later referred to as "Don Mon", or Mon The Elder, and sometimes erroneously credited as Ramón in songwriting credits) and his oldest son, Efraín Rivera Castillo (1924-1978),[1] (referred to early in his career as "Moncito"