The valley encompassing La Trinidad was originally called "Benguet", a thriving community of Ibaloi migrants from Tinek. Colonial influence reached the area upon Spanish explorers Don M. Quirante's discovery of the valley in 1642, and Guillermo Galvey's expedition to Benguet in 1829.
The valley was later renamed to "La Trinidad" in honor of Galvey's wife. Together with 40 other smaller surrounding rancherías, La Trinidad was placed under the jurisdiction of the newly established Benguet commandancia politico-militar in 1846 and was established as its administrative headquarters during the Spanish Conquest of the Philippines.
With the establishment of Benguet as a province under the Republic of the Philippines in 1899, La Trinidad was made as its capital.
In 1900, the American colonizers arrived, and La Trinidad was established as one of the 19 townships under Benguet province, upon the issuance of Act No. 48. For a brief period, Baguio became the capital of Benguet when appointed Benguet province civil governor H.P. Whitmarsh moved the capital from La Trinidad to Baguio in 1901. La Trinidad was made the provincial capital again in 1909, after the Baguio township was abolished and converted into a chartered city.
In 1942, Japanese soldiers occupied La Trinidad, Benguet.
On May 3, 1945, The Filipino soldiers of the 2nd, 11th, 12th, 13th, 15th and 16th Infantry Division of the Philippine Commonwealth Army, 1st Infantry Regiment of the Philippine Constabulary, and the 66th Infantry Regiment of the United States Armed Forces in the Philippines - Northern Luzon or USAFIP-NL liberated La Trinidad.
La Trinidad was transformed into a full-fledged town from its former status as municipal district by virtue of Republic Act No. 531, approved June 16, 1950.
The town landed on the Guinness Book of World Records for baking the world's largest strawberry shortcake, at 21,213.40 pounds (9,622.24 kg), at the La Trinidad Strawberry Festival on March 20, 2004.
In March 2015, 6,000 slices of strawberry cake were served as part of the events at this municipality's Strawberry Festival. The cakes for the slices were prepared using fresh strawberries.
On June 23, 2016, La Trinidad was highlighted in the media when the first and largest community artwork in the Philippines, the STOBOSA Hillside Homes Artwork was unveiled, featuring hillside houses within the sitios of Stonehill, Botiwtiw and Sadjap of Barangay Balili painted with sunflower and abstract designs.
La Trinidad is located at 16°28′N 120°35′E, at the central portion of Benguet. It is bounded by Tublay on the north-east, Sablan on the west, Baguio City on the south, Itogon on the southeast, and Tuba on the south-west.
According to the Philippine Statistics Authority, the municipality has a land area of 70.04 square kilometres (27.04 sq mi) constituting 7000252990000099999♠2.53% of the 2,769.08-square-kilometre- (1,069.15 sq mi) total area of Benguet.
The terrain is generally mountainous with springs, rivers and creeks. The town has a valley which encompasses several barangays. The valley floor elevation is at 1,300 metres (4,300 ft) above sea level. Elevation ranges from 500 to 1,700 metres (1,600 to 5,600 ft) above sea level.
Balili River is the municipality's main water drainage which carries upstream water from Sagudin River in Baguio City. The river merges with another upstream river in Tuel upon reaching the La Trinidad-Tublay-Sablan tri-point.
La Trinidad belongs under the Type I climate by the Coronas System of classification with distinct wet and dry seasons. The dry season is from November to April while the wet season occurs during the rest of the year. The climate is cool with temperatures ranging from 11.7 °C (53.1 °F) during the month of December at its coldest and 23.2 °C (73.8 °F) at its warmest during the months of March, April and May. The average daily temperature is 18.55 °C (65.39 °F). Wind velocity is 1.43. During the rainiest month of August, the rainfall average is 850.70 millimetres (33.492 in).
La Trinidad is politically subdivided into 16 barangays., with 11 classified as urban and 5 as rural. As of 2015, the most populous is Pico with 23,282 people, while Bineng, with 1,624 people, has the least. Wangal is the largest in terms of land area, while Cruz is the smallest. Balili was the most densely populated, and Bineng was the least. Bineng has the most number of sitios, while Betag has the least with only 4.
In the 2015 census, La Trinidad had a population of 129,133. The population density was 1,800 inhabitants per square kilometre (4,700/sq mi).
In the 2016 electoral roll, it had 39,607 registered voters.
La Trinidad supplies most of the Philippines' strawberries and cut flowers which include roses. The La Trinidad Vegetable Trading Post is visited by wholesalers and traders of vegetables from other provinces. The presence of the Benguet State University in the municipality serves as a boost to agricultural research and development in the region.
Its proximity to the city of Baguio attracts tourists, primarily to the strawberry fields in the valley, and lesser to the Benguet Provincial Capitol and the Rose Gardens of barangay Bahong.
La Trinidad, aside from the adjacent city of Baguio, is the center of higher education in Benguet province.
As of 2014, La Trinidad has 23 public elementary schools and 7 public secondary schools.
The main campus of the Benguet State University, the first university in the province, is located in the municipality.
La Trinidad is the burial place of:Deodato Arellano (1844–1899), a Filipino patriot and one of the founders of the Katipunan.