David -
Click on the "Archives" button and that will reveal approx 18,000 messages from 2006 to 2009. Once in "Archives" you can click the "Stats" which is a different set than for the current board page. And, yes it seems that there must have been lots of messages predating the archived set.
John
p.s. many of the larger pages (e.g. Mississippi, Arkansas) have valuable "Archive" sections.