>How can one make a SF SD starter from scratch unless they make it in SF?<

one can't really, Bob. The best SF starter used to come in a packet called
San Francisco Sourdough starter, it cost about a buck fifty, but I haven't
been able to find it lately. (Now, before everyone writes in all hot and
bothered about my use of the word "best"- to qualify I was a rank beginner,
and this packet made up really tasty bread for me.) It really worked well to
use a fresh batch of SD yeast with each batch of bread, one got the best
flavor that way, instead of keeping it as a starter in the fridge, or
freezer. I have tried making a local sourdough starter, though, with San
Antonio yeast, and it worked out ok. Healthy, strong, with a good winey
smell. The best though turned out to be the starter for the barm on the
Lionel Poilane loaf. You start with a 1/4 cup cracked rye, and some whole
wheat flour, water, and yeast, and let it cook up until bubbly and double,
(it also gets very slack), and then keep throwing away half and making more
until it doubles and bubbles within a 6 hour period. The yeast shows up very
strong that way, and it has a wonderful winey odor. I used the barm method
in Maggie Glazer's book, I think. Wonderful text. I bet the library has it,
if you don't.
The rye is what makes the wonderful sour dough.
For real SF there are some great yeasts out there, I know King Arthur sells
several, and there is some website which has something like 15 or more,
including an egyptian one? I think.
gw