Established on 20 October 2004,[1] it houses a representative sample of the steppe and Patagonian coast biodiversity in good state of conservation, as well as several paleontological sites of high value.

The French boat Jeanne-Amelie, authorized by Avellaneda's administration, was boarded and its crew imprisoned by the Chilean forces, an incident that worsened the bilateral relationship.

Two years later Chile once again seized a vessel in Monte León: this time it was the United States' ship Devonshire, and the action put both countries at the verge of war.

Francisco P. Moreno, naturalist and creator of the Argentine National Park System, and the paleontologist Carlos Ameghino explored the area in the late 19th century.

Monte León consists of high sandstone cliffs, rock formations, islands, wide beaches interrupted by narrow bays, and sandbars that are uncovered in low tide.

In 1880, Carlos Spegazzini, the founder of botany in Argentina, identified several hitherto unknown grass species when researching the area as part of a scientific expedition financed by Italy.

The park is also home to several large mammals, including sea lions (forming populous colonies), southern right whales, pumas and roaming herds of guanacos.