What is the plot of "The Celebrated Jumping Frog of Calaveras County"?

There is not a lot of plot to this -- it is mainly an
excuse to have a few funny tall tales about a gambler in the West in the late
1800s.

The narrator, Mark Twain, goes looking for a man
named Leonidas Smiley.  When he asks about Smiley, a man in a bar starts telling him
about some other guy called Jim Smiley who was an eccentric gambler.  He tells Twain
about all the crazy things this guy would do to gamble.

The
longest story is about how Smiley had a champion jumping frog that he would bet on. 
Someone got the frog to swallow a bunch of lead shot to weigh it down and so Smiley lost
his bet.

Eventually, Twain gets tired of hearing these
stories and leaves without finding out about Leonidas Smiley.