A century ago Arthur Pigou published The Economics of Welfare. Within this volume are a few lines relating to the pricing of traffic congestion. Over the years, these lines have attracted the attention and thoughts of some of the leading economists of their day. These have included Knight, Clapham, and Robertson in the 1920s; Kahn and Viner in the 1930s; Ellis and Fellner in the 1940s; and Buchanan, Vickrey, Solow, Friedman, Walters, Demsetz, Newbery, and Allais in the post-World War II period. Here, I look at the academic arguments from the 1920s concerning how roads should be priced and by whom. I then move to consider the continuation of the intellectual debates after World War II and their implications for policy design and implementation. Finally, I briefly look at the extent to which some of the existing road congestion pricing systems meet the requirements of the economic theory.