This dissertation tackles, head on, two fundamental questions: What is human systems integration (HSI) and how should one think about HSI problems? The objective was to develop a coherent systems method to improve the integration of HSI domains to create sustainable systems while preserving system stakeholder preferences. This dissertation addresses these questions by accomplishing two things: 1) extracting the lessons learned from a historical analysis of the emergence of HSI both as a philosophy and as a Defense Department program, and 2) using those lessons to characterize and illustrate a technical approach to addressing HSI considerations early in an acquisition process. It is shown that the discourse on general systems that occurred over the latter half of the twentieth century, coupled with pressing organizational factors within the U.S. Army, were the principal forces that shaped and drove the emergence and formal recognition of HSI. As determined from this historical analysis, HSI involves the integration of the behavioral sciences, human factors engineering, and operations research to more broadly represent human considerations in early weapon system analyses and the products that evolve from these analyses. Inclusion of HSI in system analyses necessitates a holistic perspective of the performance and economic trade space formed by the synthesis of the HSI domains. As a result, individual domain interventions are considered in terms of tradeoff decisions. Ideally, the HSI trade space can be systematically explored by integrating Simon's research strategy, Kennedy and Jones' isoperformance approach, and coupling isoperformance with utility analysis through means such as physical programming. Although domain tradeoffs are a central element of HSI, very few studies illustrate the integration of the behavioral sciences and human factors engineering with the tools and methodologies of operations research. Accordingly, three case studies are presented: a preexisting opportunistic dataset of potential Air Force unmanned aircraft pilots, a prospective dataset of Army Soldiers in Basic Combat Training, and data derived from simulation of staffing and shift scheduling solutions using a biomathematical model. Lastly, guidelines for a New HSI method and future challenges are discussed.