As I recall, many of these differences came from a spelling-simplification movement in the US in the early 19th century. Wikipaedia has this to say: Many of the differences were introduced into the by 's dictionary; he was a strong proponent of for a variety of reasons, both nationalistic and philosophical. There were many advocates of spelling reform in as well, but the influences of those who preferred the (or ) spellings of certain words proved decisive.
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