Focuses on the foundations laid by the early research on agglomerations, industrial districts, and industry clusters that was published in the 20th century. The sections that follow review the literature on agglomerations, industrial districts and industry clusters beginning with an introductory overview of Marshall's (1920) and other significant works in Section 1. Section 2 proceeds with an overview of themes in the literature, the geographic regions, and commonly researched industries. Sections 3 through 6 explore the themes that emerged across the decades.

The monograph concludes with reflections on the body of literature that emerged during the 20th century in Section 7.