This second of three parts of the history of the St. Anthony Falls Laboratory (SAFL) at the University of Minnesota documents the transition to increased emphasis on environmental research. SAFL methodology includes laboratory experimentation and field observations, physical model studies and numerical simulations, and stochastic data analysis. Much of the research at SAFL has been connected to hydraulic structures, renewable energy, protection of the environment, and geophysical fluid dynamics. From its beginning in 1938, SAFL has been an interdisciplinary science and engineering research and educational facility with a strong grounding in fluid mechanics. Starting in the 1960s and 1970s, when awareness and legislation of environmental impacts of human activities grew dramatically, SAFL's research expanded significantly into areas connecting fluid mechanics with the chemistry and biology of aquatic environments, and into geophysical (earth-surface) processes. Environmental research at SAFL began with water resources engineering and riverine sediment transport. After developing and applying techniques of physical model studies for hydraulic structures and high-speed marine propulsion, SAFL researchers developed numerical flow and water quality simulation models for the protection of aquatic environments. Studies on the influence of fluid flow on pollutant transport and the growth and behavior of organisms were initiated. Geophysical processes became a centerpiece of SAFL research with the creation of the National Center for Earthsurface Dynamics (NCED), which got a home at SAFL in 2002. Fluid flow in the human body has been studied in co-operation with medical professionals. Field-scale experimentation was added for environmental and geophysical studies. Sophisticated experimental facilities and data acquisition and simulation tools have been developed by SAFL researchers. Examples of environmental research and design studies that have been conducted at SAFL since its opening in 1938 will be presented in nine major research categories: urban storm water runoff and water quality; environmental transport and mixing; water quality dynamics and modeling; global climate change effects; protection of fish and fish habitat; eco-and bio-fluid mechanics; watershed eco-hydrology and the Outdoor Stream Lab; sediment transport, earth surface dynamics, and the NCED legacy; and innovations in instrumentation and data acquisition. Examples will showcase the evolution and significance of environmental research at SAFL. The outlook for environmental research at SAFL and its connection to renewable energy will be presented in Part 3 of the presentation.