Why did Bud keep rocks in his suitcase in Bud, Not Buddy?

Bud keeps rocks in his tattered suitcase because they are a memory of his deceased mother. At the beginning of the book, the reader does not understand the exact significance of the rocks with the writing on them. The reader simply knows that these rocks are a memory from Bud’s mom and that he keeps them in this treasured suitcase along with the picture of his mom and the flyer advertising Herman E. Calloway’s band performance. As the story progresses and Bud actually meets Herman E. Calloway, the reader realizes that the markings on the rocks are actually performance dates for the jazz band. Bud’s mom saved these rocks from the performances she attended (taken from each place the jazz band played) and passed them on to Bud as a special remembrance of his family. It is a touching gesture in Bud, Not Buddy when Bud offers these rocks to Calloway after finding out that Calloway is, in fact, his grandfather.

Why did Bud keep only one rock in 'Bud, Not Buddy'?

Bud carries several items within his suitcase at all times as he journeys to Grand Rapids, Michigan in hopes of finding his father. In his suitcase, Bud carries fives small rocks, which have locations and specific dates written on them.

When Bud arrives at Grand Rapids, he meets Herman Calloway, who seems too old to be his father. While Bud is riding in the car with Herman, he discovers similar rocks with locations and dates written on them in Herman's glove compartment. Herman then notices that Bud has the same type of rocks that he used to give his daughter as keepsakes and realizes that Bud is his grandson.

Herman is overcome with emotion after learning about his daughter's death, and Bud realizes that he has been carrying his mother's memories inside him all along. At the end of the novel, Bud gives the rocks back to Herman because he feels like they would mean more to him. However, Bud keeps one rock that has Flint written on it, as a token of where he grew up.