US multinational firms are crucial actors that shape and sustain the rules of the world order. They inherit the advantages conferred by US informal power and generally guide the substance of US foreign economic policy. When they expand abroad to take advantage of the opportunities provided by international rules, their foreign investments anchor their interests and lead them to build political influence. Multinationals do not always win; but the main constraints on their power arise within the US political system. They generally prevail when they credibly link their private interests to public interests and generally fail when their profits clash with prevailing elite views of national security. This book presents sophisticated economics in readable terms and traces a detailed history of the emergence of order in trade, finance, decolonization, development, property rights and intervention since 1945 and into the twenty-first century.