Founded in 1870, and incorporated on April 9, 1888, San Jacinto is one of the County's oldest communities with roots that stretch back to the earliest days of California.

Because of it's mild climate and fertile land, the region became home to Native Peoples, Spaniards, Mexicans and Americans - all of whom have made a unique and indelible imprint on the character of the valley.

The first native people settled in the San Jacinto Valley thousands of years ago. Later, the Serrano and Cahuilla people arrived. Their villages were located along and near streams and springs. They were hunters and gatherers and they subsisted primarily on small game and acorns. The Soboba Indian Reservation, just east of San Jacinto, is now the home to the descendants of some of these people.

The first Spanish explorers entered the San Jacinto Valley in the early 1770's. In 1774, and again in 1775, Col. Juan Bautista de Anza led two expeditions up from Mexico, crossing the Colorado River at Yuma and continuing across the Borrego Desert and up Coyote Canyon.

During the 1870's, a little town began to grow up around Procco Akimo's store. This community was located south east of modern downtown San Jacinto, on what is now Hewitt Street.

After the Estudillo lands were broken up in the early 1889's, a group of Los Angeles investors organized the San Jacinto Land Association, which acquired some 15,000 acres of the old ranch. In 1883, they laid out a rival town site less than 2 miles away.

For several years, "Old" San Jacinto and "New" San Jacinto struggled for dominance. The battle was not settled until 1888, when the Santa Fe railroad built a branch line into the Valley from Perris, which terminated on the west side of "New" San Jacinto on land donated for the purpose by Francisco Estudillo. "Old" San Jacinto was far from the tracks and eventually faded away. The new City of San Jacinto was incorporated that same year on April 9, 1888.

By the 1870's, the Valley's economy had moved from cattle ranching to horticulture. Early ranchers had grown grain, then apricots, walnuts and citrus production came to dominate the area. Turkey ranching and dairy farming came later. Besides agriculture, several local lime kilns added to the local economy before World War I.

Tourism also had an impact on the Valley, beginning around 1900. Natural hot springs along the north side of the Valley stimulated the development of several tourist resorts with hotels, guest cabins and bath houses. Gilman Hot Springs was the best-known resort. It was originally developed in the 1880s, and was acquired in 1913 by the Gilman family, who ran the resort for 65 years. Soboba Hot Springs was also popular, with its Indian-style cottages scattered along the hillside. Further west was Eden Hot Springs.