Blame Noah Webster.
Saturday is the Fourth of July, also known as the American holiday Independence Day. I'm American and I think it's fair to say we love the British now--we give British royalty a royal welcome when they visit America--but Saturday is the day we celebrate our independence from Britain, and people often ask me why there are differences between American and British English, so this seems like a good time to answer that question.
Why Do Britons and Americans Spell Words Differently?
The first question is why are British and American spellings different for certain words?
The first answer is to blame Noah Webster, of Webster's Dictionary fame. He believed it was important for America, a new and revolutionary nation, to assert its cultural independence from Britain through language. He wrote the first American spelling, grammar, and reading schoolbooks and the first American dictionary. He was also an ardent advocate of spelling reform and thought words should be spelled more like they sound.
Many years before he published his well-known American Dictionary of the English Language, he published a much smaller, more radical dictionary he called a Compendious Dictionary that included spellings such as w-i-m-m-e-n for "women" and t-u-n-g for "tongue." That dictionary was skewered and he dialed down the spelling reform in his final masterpiece. Yet still, Noah Webster, his affection for spelling reform, and the success of his final dictionary in 1828 are the reasons Americans spell words such as "favor" without a "u" (1), "theater" with an "-er" instead of an "-re" at the end, "sulfur" with an "f" and not a "ph" in the middle, and "aluminium" as "aluminum (2)."
Next: Differences That Weren't Created by Webster