This article reconstructs the history of mutual assistance among Federal Reserve Banks. We present data on accommodation operations through which Reserve Banks mutualized gold reserves in emergency situations between 1913 and 1960. Reserve sharing was important in response to liquidity crises and bank runs. Such cooperation was essential for the cohesion of the U.S. monetary union. But fortunes could change, with emergency recipients of gold becoming providers. Because imbalances did not endlessly grow, instead narrowing when region-specific shocks subsided, mutual assistance created only limited tensions. These findings speak to the current debate over TARGET2 balances in Europe.