In the case of Mare Island Parts it was the West Coast Rework Facility for Fast Attack Submarines and before that a lot of the WWII Liberty Ships were manufactured there and they did it to facilitate traffic flow down the Napa River to the greater SF Bay. It was a great place to work for a couple of years after I got out of the USN. Being a Marine Electrician was cool. It is too bad M.I.N.S.Y. was shut down, it was a critical part of the US Military machine for 150 years.