Before the arrival of the Spanish, the coastal plains in northwest Luzón from Bangui in the north to Namacpacan in the south were a region called the Ylokos.

The pressure of increasing population and the need for land made the people thrifty, and they built their villages near small bays and coves called looc in the local dialect.

The Ilocos region was a thriving and fairly-advanced cluster of towns and settlements familiar to Chinese, Japanese, and Malay traders when the Spanish explorer Juan de Salcedo arrived in Vigan on June 13, 1572.

Sent by Miguel López de Legazpi to explore the island of Luzón, Salcedo founded Ciudad Fernandina in 1574 in Bigan, in present-day Ilocos Sur.

Due to Salcedo's efforts, the settlements in Tagurín, Santa Lucía, Nalbacán, Bantay, Candón and Sinayt were pacified and paid tribute to the King of Spain.

[9] Vigan, almost four centuries old, was once known as Kabigbigaan (from biga, a coarse, erect plant with large, ornate leaves that grows on riverbanks).

It was somewhat prosperous, trading with the Chinese and Japanese who brought jars, silk and crockery through the nearby port of Pandan, Caoayan.

Affluent citizens of Vigan stocked their homes with statuettes of brass and iron, dinnerware, and other artifacts of European civilization, including fine ivory, inlaid furniture, and Chinese wares.

[10] Salcedo bequeathed his encomienda to a select group who continued the tenancy system which developed into the practice of caciquism, landlordism and usury.

Resentment of free labor triggered sporadic revolts, and those who refused to be slaves or tenants left the region for Abra and the Cagayan Valley.

Ilocos Sur's population density was 492 per square mile at the height of migration, which made it the most densely-populated region in the Philippines except for Manila.

With the operations of the Royal Company of the Philippines (Real Compañía de Filipinas), the textile industry was developed on a large scale and the abolition of the tobacco monopoly accelerated economic progress.

The beginning of Spanish rule to the first decade of the nineteenth century was characterized by revolts against tribute, forced labor and monopolies.

After Diego Silang's assassination on May 28, 1763, his wife Maria Josefa Gabriela continued the fight until she was captured and hanged on September 20, 1763.

[13] On March 25, 1898, Isabelo Abaya began an uprising in Candón and raised a red flag in the town plaza as a response to Spanish abuses and oppression.

In Cervantes, the Battle of Bessang Pass was fought between Tomoyuki Yamashita's forces and the U.S. 21st Infantry; it was the greatest victory by Filipino guerrillas over the Japanese Imperial Army in World War II.

[15]: "46" Some of the frustrated protesters then opted to pursue an armed resistance against the dictatorship,[15]: "47" [18] many of whom only returned to peaceful life after the Marcoses were finally deposed by the civilian-led People Power revolution of 1986.

[17] Public opinion compelled Marcos to investigate the incident and arrest Crisologo's son Vincent, who was reported to be the leader the saka-saka at the time.

[17][16][15]: "51" Shortly after his reported meeting with Marcos,[15]: "51"  Crisologo was killed on 18 October 1970 after being shot in the head while kneeling inside Vigan Cathedral during a church service, by a gunman who stood directly behind him and then escaped among terrified churchgoers.

[17] When the People Power Revolution which ended on February 25, 1986 deposed Ferdinand Marcos from power, and installed Corazon Aquino as the new president of the Philippines,[27][28] a provisional revolutionary government was set up in the country, and newspaper publisher Jose G. Burgos Jr. was appointed OIC Governor until a new constitution could be ratified and new officials elected.

14 which restricted the movement of people to and from Ilocos Sur, mandated the establishment of checkpoints and conditions for transportation and travel, prohibited social gatherings, encouraged flexible/alternative work arrangements or suspension of work, suspended tourism, prohibited hoarding, delineated rules for business establishments, and imposed a curfew.

The southernmost portion in Cervantes is wet with rain evenly distributed throughout the year while the southeastern part of Sugpon receives less precipitation.

[citation needed] Ilocos Sur is inhabited mostly by Ilocanos belonging to the third largest ethnic group of Austronesian origin.

[citation needed] Father Juan de Medina noted in 1630 that the natives are 'the humblest and most tractable known and lived in nest and large settlements'.

[citation needed] Other religious beliefs are represented by other Christian Churches such as Baptist and Iglesia ni Cristo wherein the largest minority has 80 plus lokal or kapilyas and barangay chapels built in the province with 8% adherence as of the mid year 2024 the church has 2 subdivided districts(Candon City and Ilocos Sur In Northern portion) in the province , Methodist, Seventh-day Adventist, and other Evangelical Christians, as well as Muslims.

Ilocos Sur's economy is agrarian, but its 2,647 square kilometres (1,022 sq mi) of unfertile land is not enough to support a population of 338,579.

The rapidly growing population, the decreasing fertility of the soil, and the long period between the planting and harvesting season, have forced the people to turn to manufacture and trade.

[58] Weaving is the most extensive handicraft, once bolstered by the installation of the NDC Textile Mills in Narvacan which supplied the weavers with yarn.

Chapters of Philippine history and religion are found in the Crisólogo collections which includes family heirlooms, centuries –old "santos" (religious statuettes made of wood or ivory)[clarification needed], other ivory images, Vienna furniture, marble-topped tables, ancient-carved beds, rare Chinese porcelains, jars and jarlettes, lamps, Muslim brass wares, and Spanish and Mexican coins.

UNESCO describes, "[the] unique architectural style [of the churches] is a reinterpretation of European Baroque by Chinese and Philippine craftsmen.