Answer:
The Gilded Age was characterized by really fast industrial and economic growth, from the 1870s to the 1900s. It was named after Mark Twain's and Charles Dudley Warner's novel The Gilded Age: A Tale of Today, which satirically describes a difficult period of living, covered and hidden with gold gilding.
The rapid expansion of industrialization was accompanied by a huge advance in transportation (railways), technologies and manufacturing (heavy industry, factories, coal mining), causing huge expansion of immigration from Europe to America, high real wage growth and individual wealth. During these years, the U.S. economy had the fastest rate of growth, with high GDP, capital formation, real wage, etc.