La union was carved out from the nine (9) towns of Pangasinan, three (3) of Ilocos Sur and villages of Eastern Pais del Igorotes (now Benguet) in the Cordilleras. It was formally created by a royal decree issued by Queen Isabella of Spain on April 18, 1854. Thus, La Union is the unification of the three contiguous geographical territories in the northwestern Luzon of Region 1. It has become the melting pot of the three hardy ethnic groups: Ilocanos, Pangasinenses and Igorots.

The insatiable quest for gold by the Spanish colonizers led them to a thriving community now referred to as La Union in 1572. The area was then an ancient trading center for gold by Asian traders notably the Chinese.

The Augustinians were the first missionaries to build towns along the coast and converted the residents to Christianity. Due to its proximity to the upland gold mines, the region became a control center for the Spanish colonizers to exploit the natives for their gold.  In 1661, Andres Malong of Pangasinan tried to snatch La Union from the Spaniards but was later defeated in Agoo.

In the late 1700s, Ilocano immigrants moved to the region to look for greener pastures, thus forming the majority inhabitants. Presently, La Union is still young compared to the older provinces such as Pangasinan, Ilocos Sur and Ilocos Norte. It is a Class-A progressive and developing province. The original dozen towns have grown to nineteen (19) municipalities and a city. Economic progress has been noticeably faster in the coastal towns while the inner towns are being challenged to cope with the dynamic pace. In the late 1900s, the national leadership declared La Union as one of the archipelago’s 12 regional administrative centers.