Nutrient pollution and climate change can lead to eutrophication and harmful algal blooms (HABs) in freshwater ecosystems. Water quality managers and other stakeholders are concerned about mitigating HABs because they sometimes produce toxins that can be harmful to humans, domestic animals, and wildlife. While most research on eutrophication has been conducted in human-dominated watersheds, HABs have recently been reported in relatively undisturbed lakes in the high-elevation Western United States, suggesting that eutrophication can occur in unexpected lakes and may be increasing. However, very little is known about productivity trends in the Western US and the drivers of excess algal production in this region. We used a combination of remote sensing and field sampling approaches to understand algal blooms in the Western US, including a) whether lakes are becoming more eutrophic, b) what factors drive eutrophication, c) how HABs influence higher trophic levels and ecosystem function, and d) when HABs are most toxic. Remote sensing records dating back to the 1980’s suggest that most lakes have remained similar in their productivity over several decades, followed by lakes that have become bluer or more oligotrophic, followed by few lakes that have become greener or more eutrophic. A variety of lake and landscape features were important drivers for these trends, including watershed land use, elevation, lake size, temperature, and precipitation. We observed physical, chemical, and biological changes in our field samples that were associated with onset of algal blooms late in the summer, including shifts in water chemistry and zooplankton communities. Finally, we outline ongoing to work to explore where and when cyanotoxin production is highest. Overall, this work complements studies suggesting that lake water quality has been relatively static for the past few decades and demonstrates the utility of regional-scale analyses to understand drivers of lake ecosystems in unique environmental contexts.