The four related tales all chronicle the maturation and loss of innocence of the adolescent Jody Tiflin and his life in Salinas Valley.  
Parts one and two of this book, "The Gift" and "The Great Mountains," were first published in the North American Review.  Part three, "The Promise," came four years later in 1937, and the final section, "The Leader of the People" followed soon after.  The young protagonist is mentored by his grandfather and Billy Buck, the only hired hand on the protagonist's father's ranch.  The four related tales all chronicle the maturation and loss of innocence of the adolescent Jody Tiflin and his life in Salinas Valley.  FTP, name this John Steinbeck novel that is not, as the title would suggest, primarily about a horse.
Parts one and two of this book, "The Gift" and "The Great Mountains," were first published in the North American Review.  
The Red Pony