Heart of the West: San Francisco as a PostaI Hub From 1849 to 1869.
I came across this while hunting out some references on early US postal history. Stunning early covers. I want one of everything. Link below should take you to the pdf. Give it time to download, it took about 30 seconds on my mac.
http://www.rfrajola.com/swlondon/SWL.pdfEnjoy
Terry