This study is an interpretation of the early computer industry in America from the perspective of evolutionary economic geography. We analyze the County Business Patterns microdata files for the 1970s and identify a variety of early computer clusters. We explore the economic factors that led to the formation of these clusters, including preexisting conditions and Marshallian externalities, and suggest that a combination of these factors goes a long way toward explaining the location patterns we observe in the data. Part 1 of our study analyzes the clustering patterns of the early computer industry. Part 2 develops explanations for those patterns. That article will be published in the next issue of Information & Culture.