"American English and British English (BrE) differ at the levels of phonology, phonetics, vocabulary, and, to a lesser extent, grammar and orthography. The first large American dictionary, An American Dictionary of the English Language, was written by Noah Webster in 1828; Webster intended to show that the United States, which was a relatively new country at the time, spoke a different dialect from that of Britain."
"Noah Webster (October 16, 1758 – May 28, 1843) was an American lexicographer, textbook author, spelling reformer, word enthusiast, and editor. He has been called the “Father of American Scholarship and Education.” His “Blue-Backed Speller” books were used to teach spelling and reading to five generations of American children. In the United States, his name has become synonymous with dictionaries, especially the modern Merriam-Webster dictionary that was first published in 1828 as An American Dictionary of the English Language."
http://en.wikipedia.org/wiki/American_English
http://en.wikipedia.org/wiki/Noah_Webster