1845 – The Walker Tariff act is passed by Congress

Largely a repeal of the Black Tariffs put in place in 1842, the Walker Tariff (named for Secretary of the Treasury, Robert J. Walker, its creator), reduced tariffs from 32% to 25%, one of the lowest tariffs in US history. Coinciding as it did with the UK’s repeal of its Corn Laws, it led to an increase in trade between the two nations.

Subsequently, tariffs would be reduced still further in 1857 (to 17%), but then increased back to 26% in 1861 (and again later that year, and in 1865, the latter two increases largely as a result of the expense of the Civil War).

Referenced in:
James K. Polk – They Might Be Giants