This article explains why Bank of America (and other big commercial banks and investment firms) began major environmental sustainability programs focused on loan portfolio overhauls in the early 2000s, and it assesses the efficacy of these greening initiatives. It offers the first environmental history of Bank of America, one of the largest financial firms in the world. Bank of America accumulated capital by taking advantage of state banking laws that allowed it to branch aggressively into rural communities, and it used that wealth reaped from the countryside to finance suburban sprawl that further increased its financial power. In the latter half of the twentieth century, this bank capitalized on laws that loosened interstate banking restrictions to acquire other financial firms outside California. Over time, it channeled its immense assets toward international fossil fuel investments, becoming one of the largest financiers of oil and gas enterprises in the world. In the early 2000s, these massive investments alarmed environmentalists, especially members of the Rainforest Action Network (RAN), who started to target Bank of America (and other banks) in their climate change campaigns. RAN and other organizations took such actions because banks in the United States had recently grown exceptionally powerful, thanks in part to the deregulation of the banking industry in the 1980s and 1990s. Environmental historians have largely ignored this story of bank consolidation in the era of climate change, even if environmentalists in recent years have tried to make the connection between the growing power of financial firms and our warming planet.