Complex sentence: Before the establishment of Pleasanton, in the 1850s, a Californio settlement, called Alisal was there, nicknamed "The Most Desperate Town in the West" and it was ruled by bandits and desperados.
Split into simpler sentences: Before the establishment of Pleasanton, in the 1850s, an earlier settlement, called Alisal was there. Alisal, nicknamed "The Most Desperate Town in the West" was was ruled by bandits and desperados.