This article examines the role of agents and how their brokerage activities influenced the composition, shape and size of Baring’s business networks in Argentinian railways during 1880–1905. Baring was heavily involved in Argentine sovereign and railway financing and relied on trusted agents, who acted as important conduits of information, to manage their business empire. We explore 2700 pieces of correspondence in the form of letters and telegrams to illustrate Baring’s network over time. Studying the case of Argentinian railways, the correspondences reveal the longevity of Baring’s network and agents’ brokerage roles over time in response to changing local and global economic currents. Through this rich qualitative data and network analysis, we contribute to understanding agent’s brokerage and network change over time. By highlighting the role of invisible actors in the form of agents, the article contributes to understanding infrastructure finance, financial globalisation and more generally, the global history of capitalism.