Explain why the period between 1870 and 1900 is known as the Gilded Age. Who ori

Explain why the period between 1870 and 1900 is known as the Gilded Age.
Who originally came up with the term, “Gilded Age”?
Why does the term apply to this era, according to the historians from the 1920s who first made the term a mainstream label for the 1870s to 1900 years? I need 200 words with citation and references …. No k12 citation.