Following the Civil War, America's  Industrial Revolution gave rise to huge wealth among various familes. None were richer than the famous "robber barons" of New York.    Names like Vanderbilt, Astor, Rockefeller, Fisk, Gould, and Morgan, to name but a few of the richest and most famous, amassed huge fortunes in finance, railroads, steel, and other emerging industries.
Taking advantage  of the continued migration from Europe and the poverty of the tenement areas of New York City,   the "robber barons" worked their employees seven day weeks, paid them bare minimum, and thought nothing of hiring children.
The industrialists, by comparison, lived a life of pseudo-aristocracy, often along the north shore of Long Island that became known as the "gold coast."  The area, just a short drive from New York City,  was immortalized in F. Scott Fitzgerald's novel,  The Great Gatsby. 
Today, many of the noveau riche maintain homes along one section of the old gold coast.....the Hamptons. 

Gatsby's Gold North Shore
Actually, they came to be called "robber barons" because they resorted to all sorts of illegal and questionable tactics to acquire their millions while building mansions that were reminiscent and often even duplicates, of the elaborate castles and estates of Europe. There,  they lived exclusive lives as the "barons" or aristocracy did in Europe.  
They wanted homes that contained the actual artifacts of Europe, so their emissaries were sent there to rob, borrow, or steal from the great estates and the ruins of classical Rome, France and Great Britain.
Thus, their mansions came to have a certain syymetry in that nearly all would have somewhere on the estate  classical ruins, statues of the gods and goddesses, so prevalent in Italy, as well as massive amounts of land on which their homes sat, somtimes as much as 1000 acres or more.  No home was complete without some authentic piece of architecture direct from Europe.
They imported marble and chandeliers from Europe,  built gilded stairways  inlaid with gold, and maintained  huge lawns with intricate gardens.  Of course, every house maintained a complete retinue of servants to keep the huge homes, often upward of 50 rooms, immaculate.
 The homes set far back on the property, up a winding road.  Each person's property sported a high fence with a small house just inside the gate, known as the gatekeeper's house.  There lived the man and his wife whose job, among other things, was to determine who was arriving and announce them via an intercom to the owner of the house.  
Every home had an elaborate stable of horses for hunting and pleasure riding as well as guest houses.
The gold coast residents belonged to exclusive yachting and social clubs where the requisite for membership depended entirely on one's name and money.  They sent their sons and daughters to private academies and later to the best Ivy League colleges.
Tomorrow:  The Decline of the gold coast.