Webster wrote the speller (1783) as part of a three-volume textbook called A Grammatical Institute of the English Language, which also included a grammar book (1784) and a reader (1785). He was motivated by a belief that the fledgling American nation should have a language and culture that was uniquely American, and to that end he changed the common English spelling of words and included some uniquely American words.
The speller had 385 editions during Webster's lifetime. It was originally titled The First Part of the Grammatical Institute of the English Language. but was changed to The American Spelling Book (1786) and The Elementary Spelling Book (1829). Popularly it was called the "blue-backed speller" because of its blue cover. It was the textbook standard for a century before it was pushed out by The McGuffey Eclectic Readers in the 1840s.
Webster was in his late 40s when he published his first dictionary, A Compendious Dictionary of the English Language (1806). He spent the next 18 years revising and expanding it, learning 26 languages (including Arabic and Sanskrit) to correctly identify the origins of words, and, of course, changing spelling to simplify. An American Dictionary of the English Language was published in 1828. It contained 70,000 words, 12,000 of which had never appeared in a dictionary before. Many scholars thought that it exceed Samuel Johnson's 1755 English dictionary in both scope and authority.
Webster, the spelling reformer, managed to get many of his alternative spellings into general usage but not all of them. Colour became color, gaol became jail, centre became center, publick became public but Americans rejected soop for soup, sley for sleigh, tung for tongue, and wimmen for women.
Webster's early educational texts largely secularized instruction, a distinct departure from the highly religious bent of such material before his. However, late in life, Webster became a Calvinist and was convinced of the need to Christianize America. His 1828 dictionary contained more Biblical definitions than had ever been included in a reference book. In 1833, Webster published his own edition of the Bible. It was based on the King James Version but he corrected grammar, replaced archaic words and edited it for content.