This article traces the origin of too-big-to-fail policy in modern US banking to the bailout of the $1.2b Bank of the Commonwealth in 1972. It describes this bailout and those of subsequent banks through that of Continental Illinois in 1984. During this period, market concentration due to interstate banking restrictions is a factor in most of the bailouts and systemic risk concerns were raised to justify the bailouts of surprisingly small banks. Finally, most of the bailouts in this period relied on the Federal Deposit Insurance Corporation's use of the Essentiality Doctrine and Federal Reserve lending. A discussion of this doctrine is used to illustrate how legal constraints on regulators may become less constraining over time.