Who is Joseph Tall Neck from Songs of the Humpback Whale and what is their importance?

Joseph is a gas station owner and used car dealer in Poplar, Montana, Tall Neck sports a long white braid down his back and coal-colored eyes. He buys Jane's used station wagon with 30,000 miles on it for $3000. He sells Jane a used MG convertible for $500, unaware that he has left a manila envelope under the seat containing over $600.