The nine stamps you show are all used, and show only part of the cancel, most likely from nine different locations, answering "why so many".
In the pic below are four stamps I cropped from your pic. The first two are overprinted, the first one is a bicentennial and also devalues the stamps, as does the second stamp. The other two are hand stamped O B (Official Business)in blue.
Overprints like the second are usually because of rate changes, and the post office not having that denomination.