Cagayán was one of the early provincias that existed during the Spanish Colonial Period. Called La Provincia de Cagayan, its borders essentially covered the entire Cagayan Valley, which included the present provinces of Isabela, Quirino, Nueva Vizcaya, Batanes and portions of Kalinga and Apayao. The former capital was Nueva Segovia, which also served as the seat of the Diocese of Nueva Segovia. Today, only 9,295.75 square kilometres (3,589.11 sq mi) remain of the former vastness of the province. The entire region, however, is still referred to as Cagayan Valley.
Present-day chroniclers hold that the name was originally derived from the tagay, a plant that grows abundantly in the northern part of the province. The term Catagayan, "the place where the tagay grows" was shortened to Cagayan. Perhaps more conventionally, etymological scholars hold that cagayan comes from an ancient word that means "river". Variations of this word—karayan, kayan, kayayan, and kalayan—all mean river.
Cagayan has a prehistoric civilization with rich and diverse culture. According to archaeologists, the earliest man in the Philippines probably lived in Cagayan thousands of years ago. Evidences to this effect are now convincing beyond scientific doubt to consider it as an incontestable fact.
In the classical era, Gattaran and Lal-lo used to be the home of hunter-gatherers who specialized in hunting mollusks. These hunter-gatherers have stockpiled their leftover mollusk shells in numerous sites in Gattaran and Lal-lo, until eventually, the shells formed into largest stock of shell-midden sites in the entire Philippines.
From available evidences, the Atta or Negrito - a short dark-skinned nomad - was the first man in Cagayan. They were later moved to the uplands by the Malays who eventually became the Ibanags, Itawes, Yogads, Gaddangs, Irayas and Malawegs - the natives of Cagayan - who actually came from one ethnicity. These are the people found by the Spaniards in the different villages along the rivers all over Cagayan. The Spaniards rightly judged that these various villagers came from a single racial stock and decided to make the Ibanag language the lingua franca, both civilly and ecclesiastically for the entire people of Cagayan which they called collectively as the Cagayanes which later was transliterated to become Cagayanos.
Even before the Spaniards came to Cagayan, the Cagayanos have already made contact with various civilizations like the Chinese, Japanese and even Indians, as evidenced by various artifacts and even the presence of minor to moderate foreign linguistic elements in the languages of the natives.