What’s the main time period of the story?

The story begins in the present day (that is, the 1960s, when the book was written) with the adult Billy working in Idaho's Snake River Valley. But most of the action takes place in the Ozark Mountains of Oklahoma in what is probably the 1920s. The experience of seeing a pack of wild dogs attacking a coonhound reminds Billy of his childhood in a remote, rural part of Oklahoma. The setting of his formative years is important, as this is a lonely, isolated place, where a young boy would be expected to seek companionship among animals rather than humans. With no one around for miles in such a remote rural outpost, it's no surprise that Billy establishes such a close bond with the Redbone Coonhounds. In doing so, he's not just fulfilling a desperate need for companionship, but also strengthening his connection to the natural world.