Franklin Pierce is killed in the train crash that in OTL killed his son.
King, Atchison and Seward aren't typos. There's just a higher presidential mortality rate
President David Rice Atchison strides into office in 1853.
Santa Ana marches over the border into New Mexico.
Cardigan is killed in a charge that almost destroys the British army.
John Brown attempts to assassinate Stephen Douglas, or does he?
Albert Sidney Johnston battles Nathaniel Lyon, in Kansas.
William Henry Seward is the Whig nominee in 1856, and Buchanan dies before the election.
Seward himself is assasinated, so Nathaniel Lyon is the president who leads America to war