During the 1930s, rating agencies took up a central role in regulatory supervision that they still have today. We study the process through which they received this regulatory license. The proximate cause for this changeover was the economic shock of the Great Depression. Exploring the performance of rating agencies in assessing the risks of sovereign debt, an important segment of the bond market, we show that superior forecasting capacities cannot explain the agencies’ growing importance. We argue that the agencies’ perceived lack of conflicts of interest (in contrast to other financial intermediaries) was a major factor in bringing them to the forefront of a new regulatory regime.