Joe,

I study early Texas Postal history. There was never a post office at Billiam's Creek or Peach Tree Creek. The man in San Antonio wrote the letter to a Mr. Bendy living near Billiam's Creek and spelled it phonetically, "Bellums Creek." Your relatives would have gone to the nearest Post Office at Woodville to pick up their mail at least thru 1854 and until a closer post office may have been established nearer to the Billiam's Creek community.

That would have been quite an exciting adventure for most frontier families in early Texas. Going to town to get the mail/newspapers etc. and see other people.