What is a blue back speller?

The Blue Back Speller, officially titled "The Elementary Spelling Book," was a widely used educational text in the 19th century, authored by Noah Webster. First published in 1786, it played a significant role in American education by standardizing English spelling and vocabulary. The book is known for its blue cover and was often used in schools to teach children how to read and spell. Its influence extended beyond spelling, contributing to the development of American English and literacy.