The sustainability of the US dairy industry is an increasingly significant issue. Producers are challenged with increasing the supply of dairy products to meet the demands of the growing population, whilst maintaining the tradition of environmental stewardship. Advances in nutrition, management, and genetics resulted in a fourfold improvement in dairy cow milk yield between 1944 and 2007. This allowed the US dairy industry to produce 59% more milk using 64% fewer cows and conferred considerable reductions in feed (77%), land (90%), and water (65%) use per gallon of milk. The carbon footprint of the entire US dairy industry was reduced by 41% over the same time period. The global livestock industry is thought to contribute 18% of greenhouse gases worldwide. However, this global average does not address the variability between systems. Instead, differences in system productivity demonstrate the considerable variation in potential environmental impact between dairy regions. Improving productivity arguably has the greatest potential to reduce the environmental impact of dairy production, regardless of system characteristics. As dairy industries worldwide pledge to reduce total greenhouse gas emissions, attention should be focused on a whole-system life cycle assessment approach rather than racing to find a 'magic bullet' solution focused at a specific process that may confer negative trade-offs.