Biblical scholars have employed various tools and approaches in seeking to understand the structure of the book of Isaiah (e.g., form criticism, historical criticism, thematic approaches, and biblical-theological approaches). This paper explores the contributions of an alternative approach. It examines the scribal marks and para-textual features of the earliest extant copies of the book of Isaiah, the “Great Isaiah Scroll” (1QIsaa) and other fragments of the book of Isaiah at Qumran, and considers what clues they might offer on how scribes and tradents in the Second Temple period understood the structure of the book of Isaiah. A worked example that will be discussed is the bisection of the book between chapters 33 and 34. The paper will conclude with some thoughts on how these texts might inform our understanding of the development and compilation of the book of Isaiah into its canonical form.