In 1865, France, Belgium, Italy and Switzerland signed a monetary convention (later known as the Latin Union), which provided for the intercirculation of specie between member states. Conventional analyses of the treaty (such as that by Willis) have portrayed this arrangement as a by-product of French power politics. This article seeks to reinterpret the economic nature of the Latin Union, focusing on the interrelations between trade, finance and money. I argue that the Latin Union did not foster trade integration and that, as a matter of fact, such was not its objective, according to archival evidence. Instead, I suggest that the Latin Union was the result of the growth of France as a major supplier of capital. The need to provide French investors with exchange-rate guarantees led borrowing countries to tie their respective monetary systems to that of France. This, in turn, created opportunities for international monetary action and the French franc became the ‘natural’ focal point of projects of monetary unification. This evolution, however, had structural limits which help to explain the downfall of the projects for expansion of the Latin Union.