The early history of the city can be traced back to its initial settlements by the Samtoy (Ilocano) people and a small community of Pangasinan traders who inhabited the coastal shores and riverbanks.

[6] According to historian William Henry Scott, the coastal area of the Ilocos region, including the city, served as a significant hub for gold trading with the Cordilleran (Igorot) people from the highlands.

[6] The settlers also engaged in trade with neighboring communities, such as the Pangasinan, Sambal and Tagalog peoples, as well as with foreign traders from Maritime Southeast Asia, China (particularly from Fujian during the Ming Dynasty), and Japan.

[7] Japanese traders later established a trading port in Aroo (modern-day Agoo), a northern section of Caboloan a pre-colonial polity in Pangasinan.

[8] Commonly traded goods included gold, jewelry, earthen jars (burnay), silk, rice, cotton, beeswax, honey, wine (basi), metals, and ceramics or porcelain.

[6] In June 1572, Spanish conquistador Juan de Salcedo arrived in the area now known as San Fernando, following his successful pacification of native and Japanese settlers in Aroo or Agoho (present-day Agoo).

Salcedo then continued his journey, sailing and exploring northward until he established Vigan as the administrative center of Spanish governance and influence in Northern Luzon.

[10] Meanwhile, during the calm summer months, San Vicente de Balanac suffered raids by Tirongs and Moro pirates, who abducted women and children and left widespread destruction.

Juan Sorolla, who had served as the parish priest of Bauang since 1829, was assigned to San Fernando, further cementing its religious and administrative significance.

Subsequently, on March 2, 1850, Governor-General Antonio María Blanco signed the Superior Decreto, officially establishing La Union and designating San Fernando as its capital, or cabecera.

By the late 19th century, the migration of settlers from the Ilocos provinces resulted in San Fernando becoming predominantly inhabited by Ilocanos, alongside Ilocanized Pangasinenses and Kankanai.

On September 10, 1896, shortly after the Cry of Pugad Lawin, a significant event unfolded in San Fernando when Spanish authorities uncovered a conspiracy against the colonial government.

Leading the crackdown was Fray Rafael Redondo, the Vicar Forane of San Fernando, who acted swiftly against suspected revolutionaries.

[9] Among the first arrested was Dr. Lucino Almeida, a respected community figure targeted for his alleged involvement in the revolutionary movement, which had gained momentum following the events of Pugad Lawin and the increasing influence of the Katipunan, led by Andrés Bonifacio.

San Fernando became the 13th of 29 towns and cities to witness the Spanish capitulation, with 400 soldiers, eight officers, and substantial military resources surrendering.

After a century of Spanish colonization, San Fernando was finally liberated, and for the first time since its founding on March 2, 1850, a Filipino assumed authority over the Casa Real.

Following the Philippine-American War (1899–1902), San Fernando, La Union, became a focal point of military conflicts as American forces sought to gain control.

The town witnessed significant abuses, including forced relocations, killings, and property destruction, which only deepened the people's resentment and fueled resistance.

The people of San Fernando, like many others in the Philippines, took advantage of the opportunities the Americans introduced, both politically and economically, leading to the town's progress.

Later that year, on August 14, Governor General William Howard Taft arrived at San Fernando Harbor, greeted by Don Joaquin Ortega and other local officials.

Despite the progress made under the new government, the era was not without tragedy on November 8, 1901, Colonel Juan M. Gutierrez, a native of La Union, became the last top-ranking Filipino officer publicly hanged by the Americans in San Fernando.

The American regime brought a new era of political and social change to San Fernando, replacing Spanish rule with democratic ideals while fostering significant economic development, though at the cost of local resistance and loss.

The Japanese defenders called the Hayashi Detachment, composed of 3,000 armed troops and 2,000 unarmed support forces, took hold of San Fernando and its surrounding areas and denied entry to the port of the city and a road leading to Baguio.

As part of the San Fernando-Bacsil Operations, the 1st Battalion of 121st Infantry were sent to loosen the enemy positions starting late February with the assistance of the Allied Air Force.

The Battle of Bacsil Ridge between the Filipino guerrillas and the Japanese Forces resulted in the recapture of the city of San Fernando, La Union.

[14] Although Ilocanos are perceived to have been largely silent about the authoritarian practices of Ferdinand Marcos' administration,[15][16] there were still San Fernando residents willing to express their objections its various abuses.

According to a certification from the Bureau of Local Government Finance, the municipality's average annual income for the calendar years 1994 and 1995, based on 1991 constant prices, was P 44,351,821.66.

The agricultural output of San Fernando illustrates diverse levels of food sufficiency, with rice at 31.91%, corn at 47%, root crops at 87.73%, legumes at 106.75%, fruits at 60.49%, and vegetables at 127.55%.

Additionally, the youth are represented by the Sangguniang Kabataan, which elected by voters aged 15 to 30 years old, is the ex officio eighth member is led by a chairman and its own council.

[43] The City of San Fernando offers a diverse array of attractions, including pristine beaches, scenic waterfalls, historical sites dating back centuries, churches and temples, leisure parks, shopping malls, and numerous renowned hotels and restaurants, all of which contribute to its appeal as a premier tourist destination.