Founded in 1891, the Unión Cívica Radical, generally known as the Radical Party, is the oldest national political party in Argentina. As a central component of Argentina's political history, the Radical Party has received much attention from historians. However, most accounts have concentrated on the period after 1916, when the party won its first presidential election; the formative years of the party have generally been ignored. Yet as the strongest opposition party during the 1890s, a pivotal decade in the birth of Argentina's party system, the Radical Party effected a critical development in Argentine politics: it created a system of open confrontation and political competition. This study offers not merely a revised version of the party's story but also a new perspective on the nature of the Radical Party and of the politics of the nation as a whole.