By DENNIS WYATT The final link in the transcontinental railroad was not at the much-celebrated meeting of the Union Pacific and Central Pacific on May 10, 1869 at Promontory, Utah. It was at Mossdale Crossing on the San Joaquin River. It is why as part of Manteca’s 100th year celebration as an incorporated city, the Manteca Mural Society is planning its fourth mural-in-a-day project that will feature that historic event.