The answer to this question can be found in chapter 8. Chapter 8 begins with Bud and Bugs being reunited with each other. The two boys are excited to be together again, and they head off toward one of the many shanty towns called "Hoovervilles." The boys are actually hoping to find out some information about how to hitch a ride west on a train. While in Hooverville, Bud meets Deza Malone. Bud opens up quite a bit to Deza, and he tells her a lot about his family (or lack thereof). Eventually, it is time to settle down to sleep; however, before Bud goes to bed, he checks on his belongings in his suitcase. He has a tobacco pouch in there with rocks in it. On each rock, there is a written "code" that Bud doesn't understand. The rocks say, "kentland ill. 5.10.11, loogootee in. 5.16.11, sturgis m. 8.30.12, gary in. 6.13.12, and flint m. 8.11.11." Bud's education is simply too lacking for him to know the code, but most readers will recognize the code as city, state, and date. As readers continue to read the story, we become more assured that those are the places where Herman Calloway and his band played on that particular date. It is in chapter 18 that we get to witness Calloway rock hunting and Bud discovering that Calloway's glove box is loaded with rocks that look just like Bud's rocks. The rocks help prove to Bud, Calloway, and everybody else that Bud and Calloway are indeed related. By the end of the chapter, readers know that Calloway is Bud's grandfather.

Mr. Jimmy said, "Bud, that's enough. Herman is not your father. But Angela Janet is his daughter's name. If what you're saying is true, Lord help us all, it looks like Herman might be your grandfather."