 Shortly after California became part of the United States in 1850, a series of droughts and floods crippled the region, forcing Sepúlveda and other "rancheros" to sell their holdings.In 1864, portions of the Rancho San Joaquin, and the adjacent Rancho Loma de Santiago and Rancho Santiago de Santa Ana were sold to real estate investor James Irvine, one of the founders of the Irvine Ranch.During most of the late 19th and early 20th century, the watershed was used for agriculture.