Editor’s note: The following is part of a series recapping Manteca history.Ten thousand people were on hand to witness the event that historians will probably look back on as when the seeds were planted for the dawn of the 21st century in Manteca.For over three decades, the four 15-story silos identified Manteca to millions of travelers on Highway 99 and Highway 120.Spreckels Sugar and Manteca literally grew up together with the decision by the German-born sugar magnate Claus Spreckels deciding to locate a sugar refinery in Manteca coinciding with the city’s incorporation in 1917.The once almighty Spreckels Sugar empire that helped build San Francisco, the Hawaiian economy, the port of San Diego and Manteca ceased to exist in 1997. The sugar company was diversified into other products such as elevators and had moved its corporate headquarters from the Bay Area to North Carolina. Sugar prices were dropping.