We study the macroeconomic effects of tariff policy using U.S. historical data from 1840–2024. We construct a narrative series of plausibly exogenous tariff changes – based on major legislative actions, multilateral negotiations, and temporary surcharges – and use it as an instrument to identify a structural tariff shock. Tariff increases are contractionary: imports fall sharply, exports decline with a lag, and output and manufacturing activity drop persistently. The shock transmits through both supply and demand channels. Prices rise in the full sample but fall post-World War II, a pattern consistent with changes in the monetary policy response and with stronger international retaliation and reciprocity in the modern trade regime.