In 1969 Houghton Mifflin of Boston published The American Heritage Dictionary of the English Language.
"The AHD broke ground among dictionaries by using corpus linguistics for compiling word-frequencies and other information. It took the innovative step of combining prescriptive information (how language should be used) and descriptive information (how it actually is used). The descriptive information was derived from actual texts. Citations were based on a million-word, three-line citation database [the Brown Corpus] prepared by Brown University linguist Henry Kucera" (Wikipedia article on The American Heritage Dictionary of the English Language, accessed 06-07-2010).