Caparra was the name of a city in Spain, and at the request of a friend of Juan Ponce de León, he gave the name of Caparra to the first Spanish settlement founded on the island. Caparra was founded in 1509, being the residence of Ponce de León, his wife and children. In addition, the house was a fort for the defense of the town and a government house. 

Guaynabo was founded in 1769, after having gone through much anguish on the part of its founders who fought tooth and nail to break away from Bayamón, since on December 14, 1764, the town was given the go-ahead to be founded. However, the municipality went through an economic crisis that led to its suppression. It was not until the change of sovereignty, which occurred in 1898, that Guaynabo was able to emerge from anonymity. 

The name Guayabo, in the pre-Columbian language, means: "here is another place of fresh water", that is, the origin of Guayabo is Indian-Antillean. The Taino Indians used words to identify objects, for example, "guay" which for them means "he aqui", "na" means "place" and "abo" was for them "rivers, life or fresh water". According to history, the chief Mabó, together with his tribe, was looking for a place to establish his yucayeques and when he arrived to the area of what we know today as Guaynabo, he found the "place of fresh water" he was looking for, since Guayabo had abundant creeks and rivers. 

On the other hand, we find that the first Spanish settlement in Puerto Rico was in the jurisdiction of Guaynabo, today known as the historic Ruins of Caparra. While Pueblo Viejo was developing, further inland in what we know today as Guaynabo, estancias, haciendas and some churches were being developed. In 1769, the Parish of Guaynabo separated from the Parish of Río Piedras. It is this date that we take for the foundation of Guaynabo. San Pedro Mártir de Verona is the patron saint of the city of Guaynabo and its first parish priest was the Puerto Rican Franciscan Cosme Sánchez. 

Since its foundation, the town was governed by people of lower military or civilian rank. It was not until 1782 when it had its first mayor in the person of Don Cayetano de la Sarna. In its beginnings and for a long time the economic development of Guayabo was very slow. Its inability to cover its expenses caused a crisis in 1875, when it was decided to suppress Guayabo as a town and segregate it between Río Piedras and Bayamón. It remained divided for thirty-seven (37) years, being in 1912 when the municipality was built again. Currently, the city of Guaynabo has ten neighborhoods: Hato Nuevo, Sonadora, Mamey, Santa Rosa, Guaraguao, Río, Frailes, Camarones, Pueblo Viejo and Pueblo.