Who does the gilded age apply to?

The gilded age meant the post-Civil War era. It was the age of self-made men, people who rose from the dregs of humble beginnings to become the Bill Gates of their time. (More like Charles Foster Kane!, if you know "Citizen Kane".) Industry and factories and embly lines. The telephone and telegraph were the "Internet" of that time and electricity (especially electric light) was another important change. Look up "gilded age famous people".