The smoke stack at the State Heating Plant serves as a survey control. The top of the stack is the benchmark.
A great way to see this benchmark up close is to visit the Mission Mill Museum grounds. Access to the museum is from Mill Street, west of 14th street. Entry into the grounds is free and you can walk around behind the mill and get an up close look at the stack, at the northwest corner of the property. Alternatively, a walk down 12th street to the intersection with Ferry Street will get you close.