The first time a third-party candidate won at least one US state was in 1832.
In 1832, Andrew Jackson of the Democratic Party carried sixteen states, Henry Clay of the National Republican Party carried six states, John Floyd of the Nullifier Party carried only one state, and William Wirt of the Anti-Masonic Party also carried only one state.
The last time a third-party candidate won at least one US state was in 1968 when George Wallace of the American Independent party carried five states.
Why is it hard for a third-party candidate to win at least one US state?