Matten and Moon (2008) distinguish American and European perspectives on Corporate Social Responsibility (CSR) on the basis of their explicitness, attributing this divergence to differences in respective national business systems, but do not explain which specific institutional differences generated this divergence. This paper extends their work by arguing that the key difference was the defeat of American labour by the new giant American corporations of the twentieth century, a defeat that was itself a product of structural limits to democracy and a weak legacy of corporatist regulation. The triumph over labour gave American corporate executives a free hand in managing their workforces, but victory also brought full responsibility for enhancing efficiency and winning public acceptance. By the 1920s, executives responded by claiming to manage according to principles of social responsibilities. While explicit CSR lost relevance during the crises of Depression and World War II, it has reasserted itself since then, especially since the rise of neo-liberalism.