Antioch is among California's oldest cities. In 1848 John Marsh, owner of Rancho Los Meganos, one of California's largest ranches, built a landing in what is now Antioch on the San Joaquin River. Antioch is one of the oldest towns in California. In 1848, John Marsh, owner of Rancho Los Meganos, one of the largest ranches in California, built a landing on the San Joaquin River in what is now Antioch.