jats:p This article studies the socio-environmental history of a steel mill in Manaus, Brazil, the largest city in Amazonia. The Companhia Siderúrgica da Amazônia Sociedade Anônima, SIDERAMA, an integrated steel mill created in 1961 and liquidated in 1997 after a convoluted history of mismanagement, was part of private and public efforts to colonize the Brazilian Amazon through industrial urbanization. Exploring its impacts at a diversity of scales, the article presents it as a historical case study of planetary urbanization. The steel mill polluted the city of Manaus, and resource extraction to feed it with materials and energy disrupted environments and societies deep into the Amazon rainforest. This process underscores the global reach of urbanization during the second half of the twentieth century and the need to rethink the role of Amazonia during the Anthropocene. </jats:p>