Accounts of forum shopping have failed to appreciate the role that federal-state competition for litigants plays in the architecture of limited federal judicial power. The article traces how the logic of competition shaped three key episodes in the development of the law of forum shopping: the early framing-era debate over jurisdictional concurrency, the formation of key modern jurisdictional doctrines in the late nineteenth century, and Erie. It shows that different doctrines relating to forum shopping, far from being inconsistent, have travelled along the same arc. Together, they form an architecture of judicial competition designed to check federal courts’ share of the adjudication market, subject to Congress’s control. Based on this history, the article develops a model for analyzing forum shopping as part of that architecture. The model can revitalize structural debates in important but stale fields of law regulating litigants’ forum choices. More generally, it challenges the canonical view that federal-state forum shopping is constitutionally disfavored. And it questions past defenses of jurisdictional competition, which cast it as a mechanism for empowering the federal protection of individual rights. Forum shopping, this article shows, is an integral part of our framework of limited federal judicial power.