One man deliberately misspelled 'colour' and 'centre' to make American English distinct

Noah Webster's 1828 American Dictionary of the English Language dropped letters he saw as unnecessary British holdovers, turning 'colour' into 'color' and 'centre' into 'center'. He wanted a national identity built partly through language, and many of his simplified spellings stuck permanently in American usage.

— Noah Webster, American Dictionary of the English Language — 1828