115 years unsolved
Just prior to being sworn in as governor of Kentucky, William Justus Goebel was assassinated - shot in the chest outside of the Old State Capitol in Frankfort.
He died four days later, after signing a single proclamation.
The 1899 election was tense, and Goebel's bristly personality had made him many political enemies despite his attachment to popular causes.
The election results were still being disputed before his death, and he had been accompanied by two bodyguards after hearing rumors of an assassination plot.
Following Goebel's shooting, wild turmoil broke out in Frankfort, as a clash of executive and judicial power in Kentucky brought about a state of affairs bordering on civil war.
As Goebel lay clinging to life, Democrats threatened to use the military to enforce his orders, while Republicans used the militia to resist.
An armed conflict was averted when the Republican Taylor yielded and all legislators left the capital.
Everyone charged with the shooting was either acquitted or pardoned.
Goebel remains the only state governor to have been assassinated while in office.