The archeological remains of the Great Pajatén, show evidence of the presence of the Chachapoya culture, in the area where the Department of San Martín is situated today. During the first years of the conquest, expeditions began to head for the Amazonian region.

The city of Moyobamba, founded in 1539 by Hernando de Alvarado, was the first Spanish settlement in the jungle. Converted in spearhead of Occidental civilization in the Amazonian region, through the combined action of missionaries and explorers, Moyobamba originally had the function of military headquarter in and from which were organized and parted the expeditions to conquer and missions to evangelize.

Later on, since the 50´s and until the end of the last century, the production and exportation of straw hats and knitted shawls, allowed San Martin to enjoy a certain economic growth, with the openning of many local businesses. Finally, this wonderful department was created in 1906, to honor the memory of the Liberating Heroe Don José de San Martín and with the construction of the Jungle´s Marginal Road, in the 60´s, the important land connection was made with the rest of the country.