Mission San Gabriel was founded on September 8, 1771 by fathers Pedro Cambon and Angel Somera. The planned site for the Mission was along the banks of the Río de los Temblores (the River of the Earthquakes—the Santa Ana River). The priests chose an alternate site on a fertile plain located directly alongside the Rio Hondo in the Whittier Narrows. The site of the Misión Vieja (or "Old Mission") is located near the intersection of San Gabriel Boulevard and Lincoln Avenue in Montebello, California (known to the natives as Shevaanga). In 1776, a flash flood destroyed much of the crops and ruined the Mission complex, which was subsequently relocated five miles closer to the mountains in present-day San Gabriel (the native settlement of 'Iisanchanga). The Mission is the base from which the pueblo that became the city of Los Angeles, California was sent. On December 9, 1812 (the "Feast Day of the Immaculate Conception of the Blessed Virgin"), a series of massive earthquakes shook Southern California. The 1812 Wrightwood earthquake caused the three-bell campanario, located adjacent to the chapel's east façade, to collapse. A larger, six-bell structure was subsequently constructed at the far end of the capilla. While no pictorial record exists to document what the original structure looked like, architectural historian Rexford Newcomb deduced the design and published a depiction in his 1916 work The Franciscan Mission Architecture of Alta California.
Legend has it that the founding expedition was confronted by a large group of native Tongva peoples whose intention was to drive the strangers away. One of the padres laid a painting of "Our Lady of Sorrows" on the ground for all to see, whereupon the natives, designated by the settlers as the Gabrieliños, immediately made peace with the missionaries, because they were so moved by the painting's beauty. Today the 300-year-old work hangs in front of and slightly to the left of the old high altar and reredos in the Mission's sanctuary.
A large stone cross stands in the center of the campo santo (cemetery), first consecrated in 1778 and then again on January 29, 1939 by the Los Angeles Archbishop John Cantwell. It serves as the final resting place for some 6,000 "neophytes;" a small stone marker denotes the gravesite of José de Los Santos, the last American Indian to be buried on the grounds, at the age of 101 in February 1921. Also interred at the Mission are the bodies of numerous Franciscan fathers who died during their time of service, as well as the remains of Reverend Raymond Catalan, C.M.F., who undertook the restoration of the Mission's gardens. Entombed at the foot of the altar are the remains of eight Franciscan priests (listed in order of interment): Father Miguel Sánchez, Father Antonio Cruzado, Father Francisco Dumetz, Father Roman Ulibarri, Father Joaquin P. Nuez, Father Gerónimo Boscana, Father José Bernardo Sánchez, and Father Blas Ordaz. Buried among the padres is centenarian Eulalia Perez de Guillén Mariné, the "keeper of the keys" under Spanish rule; her grave is marked by a bench dedicated in her memory.
Well over 25,000 baptisms were conducted at San Gabriel between 1771 and 1834, making it the most prolific in the mission chain. In its heyday it furnished food and supplies to settlements and other missions throughout California. A majority of the Mission structures fell into ruins after it was secularized in November 1834. The once-extensive vineyards were falling to decay, with fences broken down and animals roaming freely through it.
The Mission's chapel functioned as a parish church for the City of San Gabriel from 1862 until 1908, when the Claretian Missionary Fathers came to San Gabriel and began the job of rebuilding and restoring the Mission. On October 1, 1987 the Whittier Narrows Earthquake damaged the property. A significant portion of the original complex has since been restored.