Juan Malarin (1792 - 1849), a sea captain from Peru, came to California in 1822. As a reward for services rendered, the Mexican Government he was made a Lieutenant in the Mexican Navy. He made Monterey his home, and in 1824 he married Maria Josefa Joaquina Estrada, a daughter of José Mariano Estrada, grantee of Rancho Buena Vista. Malarin was grantee of the two square league Rancho Guadalupe y Llanitos de los Correos in 1833, and the two square league Rancho Chualar in 1839. He also acquired Rancho Zanjones. When Malarin died in 1849, his son, Mariano Malarin, took charge of the family estate. In 1859, Mariano Malarin (1827-1895) married Ysidora Pacheco (-1892), a daughter of Francisco Pacheco, owner of Rancho Ausaymas y San Felipe.
With the cession of California to the United States following the Mexican-American War, the 1848 Treaty of Guadalupe Hidalgo provided that the land grants would be honored. As required by the Land Act of 1851, a claim for Rancho Guadalupe y Llanitos de los Correos was filed with the Public Land Commission in 1852, and the grant was patented to Mariano Malarin in 1865.