Here’s a San Joaquin County trivia question: What is the highest point in the county?It’s the 3,629-foot Mount Boardman North located southwest of Manteca/Lathrop in the Diablo Range. It is on the Alameda-San Joaquin county line near where those two counties meet Santa Clara and Stanislaus counties. Mount Boardman, to the south, was named after W.F. Boardman who served from 1865 to 1869 as the Alameda County surveyor.