What is the importance of the Gilded Age?

The Gilded Age was a period of great economic boom in American history and brought the rise of large corporations in the market.

It is widely (and wrongly) believed to be a period of laissez-faire capitalism, where the government would neither help nor hinder the free market.
However, this is an incorrect interpretation, as government actively subsidized companies and helped them become larger than they would have become in the free market (think of the railroads and of Standard Oil).

Furthermore, the government used the Sherman Antitrust Act to break up unions. This hurt capitalism because unions were fundamentally capitalistic constructs, with the early union leaders wanting to buy the means of production, not steal them. Unions are a natural creation in capitalism, with workers coming together to negotiate with their employers. Government intervention froze this market force in its tracks, cutting the free market's own internal mechanism for coming to equilibrium and fairness.

Another reason why the Gilded Age was not laissez-faire was due to a protectionist tariffs. Imported goods from foreign companies are essential to keeping domestic producers honest. Tariffs help to create monopolies which would not have otherwise arisen.