During the late 1970s and early 1980s, Leland wrote SYSTAT, the first comprehensive, statistical software package designed expressly for microcomputers. It represented an end-run around the punch cards, queues and mainframes required for statistical analysis at that time. The program was the first of its kind to include comprehensive graphics driven by a command structure of universally applicable options, foreshadowing the graphical structure that Leland would more fully develop and articulate during the 1990s. SYSTAT also was the first software implementation of the now widely used heatmap display. He founded SYSTAT, a company of the same name, headquartered in Evanston, Ill., and later sold SYSTAT to SPSS in 1995. He went on to build a team of graphics programmers there who developed the nViZn platform that produces the visualizations in SPSS, Clementine, and other analytics services. Leland wrote the seminal book on statistical graphics, his magnum opus, The Grammar of Graphics, in 1999. The Grammar of Graphics provided a new way of creating and describing data visualizations, a language — or grammar — for specifying visual elements on a plot, which was a completely novel idea that has fundamentally shaped modern data visualization. The book served as the foundation for the R package ggplot2, the Python Bokeh package, the R package ggbio and helped shape the Polaris project at Stanford University.