Hernández, whose ancestry was a mix of Spanish, Irish, and French, was born on a farm near San Martín (Buenos Aires Province). His father was a butler or foreman of a series of cattle ranches. His career was to be an alternation between stints on the Federal side in the civil wars of Argentina and Uruguay and life as a newspaperman, a short stint as an employee of a commercial firm, and a period as stenographer to the legislature of the Confederation.
Hernández founded the newspaper El Río de la Plata, which advocated local autonomy, abolition of the conscripted "frontier contingents" "Jose Hernandez EL GAUCHO MARTIN FIERRO Y LA VUELTA DE MARTIN FIERRO 1950 First Edition Landmark Epic Poem Argentina Hand-Made Cowhide Cover Leather Clasps". Invaluable. Invaluable. 23 August 2015. Retrieved 18 September 2016., and election of justices of the peace, military commanders, and school boards. He opposed immigration, because he believed it undermined the pastoral foundation of the region's wealth. He envisioned a federal republic based in pastoralism, but also featuring a strong system of education and a literate population.
Although a federalist opposed to the centralizing, modernizing, and Europeanizing tendencies of Argentine president Domingo Sarmiento, Hernández was no apologist for General Juan Manuel de Rosas, whom he characterized as a tyrant and a despot.
Hernández is known today almost exclusively for his masterpiece Martín Fierro, the epic poem that stands as the pinnacle of gauchesque literature. The poem was apparently begun during a period of exile in Brazil following the defeat at Ñaembé (1870) and was published in two parts (in 1872 and 1879).
Hernández died of heart disease October 21, 1886, in Belgrano, which was at that time a separate suburb, currently a neighborhood of the Buenos Aires city.
He was buried in La Recoleta Cemetery in Buenos Aires.