Oesterheld was born 23 July, 1919 to a Jewish-German father and Spanish-Basque mother. He wrote numerous children’s books using the pseudonym ‘Sanchez Puyol.’ In 1951 he began writing comic scripts for Cinemisterio which published his first works. Bull Rocket appeared in Misterix and in 1953 he wrote Sergeant Kirk with art by Hugo Pratt.
In 1955, with his brother Jorge, he founded the comic periodical Frontera, and wrote over 150 scripts for fifty artists. Among them were some of the finest adventure comic artists to ever walk the earth; Alberto Breccia, Hugo Pratt, Francisco Solano Lopez, and Arturo del Castillo. Oesterheld wrote the adventures of Ray Kilt, Sargento Kirk, Indio Suárez, Bull Rocket, Ernie Pike, Ticonderoga, Randall the Killer, and Sherlock Time. Mort Cinder appeared in Misterix in 1962 with art by Alberto Breccia. Frontera declared bankruptcy in 1963.
Oesterheld’s principal creation was the Kafkaesque science-fiction work El Eternauta, illustrated by Francisco Solano López, born in Buenos Aires in 1928. López and his son, who was active in the resistance, left for exile in Spain at the time of the dictatorship. The first version of El Eternauta was published from 1957 to 1959, in Hora Cero Semenal, the second version in 1969, illustrated by Alberto Breccia.