This is a list of the 100 largest cities in the U.S. State of California ranked by population, based on estimates for July 1, 2019 by the United States Census Bureau.. On average, underground aquifers provide nearly 40% of the water used by California’s farms and cities, and significantly more in dry years. Sacramento Underground tours take place in Old Town Sac., and even if you don't make it below the surface, this historic and well preserved spot offers a lot of history all on it's own. One of the most prominent cities in Northern California has a mysterious past… and a whole underground level that hardly anyone talks about! '&charset='+document.charset : (document.characterSet ? //]]>-->, ,