He was a leading figure in the period known as the Infamous Decade, characterised by electoral fraud, corruption, and rule by conservative landowners heading the alliance known as the Concordancia.

[1] Castillo graduated in law from the University of Buenos Aires (UBA) and began a judicial career.

From 1932 until 1935, he was elected to the Argentine Senate for Catamarca Province for the National Democratic Party and was also Minister of Interior.

From 1938 to 1942, Castillo was vice-president of Argentina under President Roberto Ortiz, who won the election by fraud as the head of the Concordancia.

He was overthrown in the Revolution of '43 military coup[2] in the midst of an unpopular attempt to impose Robustiano Patrón Costas as his successor.