The park comprises 4,220 square kilometres of jungle, a significant portion of which is annually flooded by the Amazon River during the wet season.

In 1970, Julia Allen Field (1927-2010), the American founder and President of Amazonia 2000, asked INDERENA (The Institute for Natural Resources, Colombia's equivalent to the U.S. Department of the Interior, now called The National Institute of Renewable Natural Resources and Environment) to establish a protected forest and wildlife sanctuary, including jaguars, around the research station she built called La Manigua on the Cothué River.

(3°10'58.8"S 70°12'00.0"W) In 1975, Julio Carrizosa, the Director of INDERENA, achieved the creation of Amacayacu National Park, an area of approximately 4,220 square kilometers of jungle.

He also courageously banned hunting for the international skin trade (e.g., jaguar, ocelot, deer), which had fueled the local economy.

On September 30, 1975, in Tarapacá, Colombia, a town closest to La Manigua, the Chief of Forestry, Fidel Castillo, and Alirio Muñoz, the town's Mayor, announced the establishment of the national park and the ban on all cutting of the forests for lumber.