According to the historian, a native of this municipality, Rafael J. Mirabal Linares, August 11 is the date on which the founding of the town of Adjunta is promulgated. So, it was born in the s. XIX. The mainly agricultural town was the second to be properly planned, according to Mirabal. Since 1888 he had an electric telegraph and, around 1894, he was distinguished with the royal title of Villa: "for the increase of his neighborhood, progress of his agriculture and development of his trade". Along with Yauco, it is one of the municipalities with the highest coffee production and, linked to that town, Adjuntas has a strong Corsican influence that is evident in the number of surnames such as: Gianoni, Saliceti, Pietri, Bianchi, Mattei, Battistini, Antongiorgi and others. The Corsicans come from the island of Corsica that was originally populated by Italy.
Hence their Italian surnames. But, as of 1768, it was ceded by Genoa to the French. In 1794 it was integrated into the French state, which explains the French names of many Corsicans and their strongly French language and culture. Today some families of Corsican origin maintain their properties on the island of Corsica. An example of this are the Pietri and Saliceti families of Adjuntas, Puerto Rico.The production of coffee intensified during the last decades of the 19th century, and it was mainly destined to the export of the grain to Europe, where it enjoyed great esteem. When some Latin American countries began to produce coffee, the price of the bean dropped considerably, and production in Adjuntas dropped. Also the cultivation of Citron, which was processed in Adjuntas and sent to European markets (Holland, France and United Kingdom). The Saliceti and Mattei families from Adjuntas worked in the production, planting and preparation of citron for many years. Also the Dutch DeJong de Adjuntas family who continued the citron business under the "Citron Export" Corporation in the Garzas de Adjuntas neighborhood. The sowing of citron reduced its production due to a strange disease that attacked the plantations of the product and affected it. A hurricane at the end of the 19th century (1898) caused extensive damage to local agriculture, which took several years to recover. United States President Theodore Roosevelt, returning from an inspection visit of the construction of the Panama Canal and after visit the Governor of the Island, he drove through Adjuntas. In one of his letters to his son Kermit, the President described his journey to the interior of the Island, noting the steepness of the mountain range and the colorfulness of the landscape: "The next morning we returned in cars on different and even more beautiful roads. The mountain made us think of a tropical Switzerland.
We had to cross two or three rivers where oxen with yoke tied to their horns pulled cars over the water. In a small village we had lunch outdoors, very good, with chicken, eggs and bread, and some wine offered by a wealthy young Spaniard who came from a nearby coffee farm. " It is believed that the allusion to Roosevelt's "tropical Switzerland" was what gave him the cognoment by which Adjuntas is known today (Caribbean Switzerland). The "City of the Sleeping Giant" is an allusion to the profile of a mountain seen from the village.