The Revolutions of 1848, the largest wave of revolutions in European history, were vital in laying the foundations for modern nations on the continent. In Italy, it started several decades of instability for members of religious orders, beginning when Pope Pius IX was forced to flee from Rome after being overthrown as ruler of the Papal States. This meant that he was unable to provide protection for the various religious in the region, including the Society of Jesus. Already unpopular across Europe, the Jesuits were forced to look for safe places to minister — which included the United States. Already, some Italian Jesuits had journeyed across the Atlantic Ocean to act as missionaries on both coasts. Soon even more Italian Jesuits would join them, when the Jesuits of the Turin Province in northern Italy were deported in 1848. By 1879, half of the members of the Turin Province and almost a quarter of the Neapolitan Jesuits lived in the US.
Several Italian Jesuits had traveled west with Peter De Smet in 1844, ministering in the Rocky Mountain Mission of the Pacific Northwest. The region was difficult, though, and there were increasing demands for Catholic priests to the south in California. Michael Accolti, SJ, and Giovanni Nobili, SJ, members of that 1844 group, traveled from Oregon to San Francisco in 1849 and began the permanent Jesuit presence in California. After spending years as guests of the Maryland Province, many of the Turin Province Jesuits were eager to find independence on the West Coast and traveled across the country to join their fellow Italians.
Until the beginning of the 20th century, the West Coast was essentially the home for exiled Turin Province members. The Rocky Mountain Mission and California became a mission of the province in 1854. In 1909, the mission officially became the California Province, and covered the United States west of the Rockies and the Territory of Alaska. The province was split in 1931: the northern states became the Oregon Province, and California kept its namesake state, the southern states west of the Rockies, and eventually the territory of Hawaii.
The California Province continued to minister and educate for another 85 years, working both in the United States and in missions of their own in Asia. In 2017, the Oregon Province and California Province rejoined to become the West Province of the Society of Jesus in the US.