Coalinga. California Historical Landmark 344, near the intersection of what are now State Routes 33 and 198, marks the approximate site of his headquarters, Arroyo de Cantua, where he was slain.The first post office was established in 1899. The city incorporated in 1906.Coalinga's water was so full of minerals, that potable water had to be brought in by railroad in tanker cars from Armona, California. For many years, "Armona Water" was the only water residents could drink. And Coalinga was one of only a few towns in the US that had three taps, one for hot water, one for cold water, and one for drinking water. Finally, in the early 1960s, Coalinga held the first practical demonstration for reverse osmosis (RO), and its Armona water was replaced by RO water.On May 2, 1983, Coalinga was struck by a 6.5 magnitude earthquake that destroyed more than 800 houses and other buildings; it was felt as far away as Los Angeles and western Nevada.