San Juan, Ilocos Sur

The town was named in honor of its patron, St. John the Baptist.

The town was established in 1772 as Lapog. Over the years, the name of the municipality went through a series of changes. The early settlers and occupants called it "Lapo", short for "Lapo-Lapo", a tall grass which grew everywhere in the area. In 1772, Don Tomas Aquino, the first local leader, initiated the organization of the scattered communities into one, calling the place "Lapog", a derivative of local vernacular "Lap-Lapog" which means unirrigated land.

It was stricken by all sorts of plagues and epidemics (like the smallpox epidemics of 1808 and 1918–19, locust infestation in 1903, and destruction of ricefields by worms called "arabas" in 1905). Bessang Pass, just south of the poblacion, was constructed in 1874. Americans destroyed their town hall in 1903. But despite these misfortunes, San Juan progressed into a prosperous community.

For 189 years, "Lapog" remained in the records as the official name of the town until June 18, 1961, when Republic Act No. 3386 was enacted to rename the town, "San Juan". Since most of the inhabitants were of the belief that religious names bring peace, happiness, and prosperity, the town was renamed "San Juan", after the name of its patron saint, Saint John the Baptist.

The Municipality of San Juan is bordered by Cabugao to the north, Magsingal to the south, the provinces of Ilocos Norte and Abra to the east.

San Juan is situated 21.42 kilometres (13.31 mi) from the provincial capital Vigan, and 422.35 kilometres (262.44 mi) from the country's capital city of Manila.

In the 2024 census, San Juan had a population of 26,709 people.^[13] The population density was 410 inhabitants per square kilometre (1,100/sq mi).

Poverty incidence of San Juan

Source: Philippine Statistics Authority^{[14][15][16][17][18][19][20][21]}

The San Juan Schools District Office governs all educational institution within the municipality.^[23]

• List of renamed cities and municipalities in the Philippines