In this final report, we present results from research conducted under Phase I of NREL contract number XCM-4-44000-01, from May 2004-January 2005. The overall goal of this project is to better understand infrastructure development strategies for widespread implementation of hydrogen as an energy carrier. Under this contract, we continued earlier research on this topic, improving simulation tools to study hydrogen transition strategies, and applying these methods to a geographically specific case study in the Midwest. We also worked as part of the USDOE's H2A group, developing models of hydrogen delivery systems. Our technical approach is to attempt to capture the site-specific nature of the H2 infrastructure design problem by use of Geographic Information System (GIS) data as a basis for understanding the spatial relationships between hydrogen demand and supply and existing infrastructure. In this study, we explored the use of mathematical programming techniques to find the lowest cost strategy for building a widespread hydrogen energy system. The goal of the study is to develop a better understanding of the entire system over time, and formulate "rules of thumb" for low-cost regional hydrogen infrastructure strategies.