The correct answer to this open question is the following.
The United States federal government changed from 1790 to 1865 in that it has to pass through a Constitutional Convention in the city of Philadelphia, Pennsylvania to create a new Constitution, and in the process, sorting out a series of debates and arguments between Federalists and Antifederalists to reach a final agreement.
Then, the concept of republicanism in which citizens play an important role in the way the government act, as well as the importance of the sovereignty of the states to have a state law and a federal law. This clearly regulated the relationships between the states and the federal government.
Then it came a time where states and federations had difficult issues to resolve that divided the country and generated a Civil War that caused much pain and destruction in the country.
It had to come a period of Reconstruction in the South to try to settle things up, with no so much success.
The laissez-faire policies of the Gilded Age maintained continuity in the United States' work and did not represent more change because big monopolies were created with the federal government's approval. That is why the Standard Oil Company of John D. Rockefeller and US Steel Company of Andrew Carnegie, became the most powerful companies in America during the Gilded Age.
The changes had to wait until the arrival of the Reformation period in the United States when muckraker journalism and social groups forced many changes in the federal government with the creation of new legislation.
