The Hydrogen Delivery program at Sandia focuses on the need for safe and reliable hydrogen transport pathways from centralized production facilities, e.g., pipelines. Carbon-manganese steels are candidates for the structural materials in hydrogen gas pipelines; however, it is well known that these steels are susceptible to hydrogen embrittlement, which compromises the structural integrity of steel components. One manifestation of hydrogen embrittlement in steel hydrogen containment structures subjected to pressure cycling is hydrogen-accelerated fatigue crack growth. Such pressure cycling represents one of the key differences in operating conditions between current hydrogen pipelines and those anticipated in a hydrogen delivery infrastructure. Applying structural integrity models in design codes coupled with measurement of relevant material properties allows quantification of the reliability/integrity of steel hydrogen pipelines subjected to pressure cycling. Furthermore, application of these structural integrity models is aided by the development of physics-based material models, which provide important insights such as the effects of gas impurities (e.g., oxygen) on hydrogen-accelerated fatigue crack growth. Successful implementation of these structural integrity and material models enhances confidence in the design codes and enables decisions about materials selection and operating conditions for reliable and efficient steel hydrogen pipelines.