ending with McKinley were quite forgettable in terms of their domestic policies.  One reason for this was that people did not think the federal government should take a major role in the lives of regular people.  Another reason was that after Andrew Johnson's impeachment, the presidency was severely weakened.  After McKinley's assassination, Theodore Roosevelt turned the presidency into what he called the "bully pulpit" for causes that he deemed important.  Roosevelt wanted to preserve the environment because he was an avid outdoorsman, so he created several national parks.  As a New York City police commissioner, he fought against corruption, so he took on corruption in business as well.  He broke up monopolies and after reading The Jungle, he sent federal investigators to regulate the food and drug industry as well as meatpacking plants. Roosevelt's handpicked successor, William Taft, broke up even more trusts but he lacked Roosevelt's forceful personality so he was replaced by Woodrow Wilson in 1912.  Wilson wanted to be known for his domestic policies, so he started to investigate Wall Street speculators and he signed legislation which ended child labor.  WWI brought about the end of the Progressive Era as Americans focused their energy on the European war and after the war Americans were suspicious of anything that looked like a leftist idea.  

The presidency did change to some degree during the Progressive Era.  In general, it became somewhat more powerful with presidents taking the lead more than they had in past times.  The major reason for this was that many people had a desire for change during this time.

After the Civil War, presidents were not very important.  There was a relatively pervasive attitude that held that presidents should not be at the forefront of the government.  That role was reserved more for Congress.  With the coming of the Progressive Era, this started to change.  People saw presidents more as the leaders of the country.

One reason for this was that the country had been fairly evenly divided in the late 1800s.  Neither party really had a strong hold on public opinion.  Therefore, it was not really possible for any president to come into office and strongly push for a given agenda.  This changed in the Progressive Era as well.  Now, there was something of a groundswell of support for reform and a president could come in and act more vigorously.

With people showing a real desire for reform, the president could take a stronger role in government.  It helped that the first progressive president was someone with a strong personality like that of Theodore Roosevelt.  But the real cause of the change was that there was now a real mandate for change that presidents could pursue.

The Progressive Era (1900–1920) was a period of significant change in the United States. One of the changes was in the nature of the presidency. It was during this period that the presidency became the modern and robust office that it is today. The presidents during this time were Theodore Roosevelt, William Howard Taft, and Woodrow Wilson.

The Progressive Era followed the Gilded Age. The Gilded Age (1878–1899) was a period of extreme economic inequality. Labor unions began to form, and there was discontent in rural areas. Another problem of this time was the growth of cities as well as slums. The three presidents of the Progressive Era tried to ameliorate some of these problems and address the challenges posed by rapid change.

Theodore Roosevelt's program for the nation was known as the Square Deal. This included railroad regulation and breaking up monopolies. He also cleaned up the corrupt meat and drug industries. Roosevelt sought to alleviate labor unrest by mediating a coal strike. He was a strong and capable leader, and he chose Taft as his successor.

Taft's character was unlike that of Roosevelt. He lacked his predecessor's charisma and zeal for reform. Sworn in in 1909, it soon became obvious that there were important differences between the colorless Taft and the illustrious Roosevelt. For example, Taft was far more cautious and legalistic in his approach to conservation. Roosevelt, unhappy with Taft, challenged him for the Republican presidential nomination in 1912.

The Taft-Roosevelt feud split the Republican vote and gave the election to the Democrat, Woodrow Wilson. Wilson called his program "New Freedom" during the presidential election. He continued his predecessors's policies of cracking down on monopolies. He presided over the introduction of an eight-hour day for railroad employees and loans to farmers. Child labor was abolished. In 1920, the Nineteenth Amendment, giving women the right to vote, was ratified.

These three presidents—especially Roosevelt and Wilson—irrevocably changed the presidency and made it the powerful branch of government it is today.

The presidency became more active during the Progressive era, more hands-on in its involvement with the running of the economy. The Progressivist movement had revealed a seedy underbelly of poverty, corruption, and rampant exploitation beneath the glittering veneer of wealth and opportunity of late nineteenth-century America. And a growing consensus emerged that only the president of the United States had the necessary power and authority to make a difference in dealing with the numerous social and economic problems plaguing the country.

Theodore Roosevelt took the Progressive ideal to heart, using the office to embark upon a substantial challenge to the power of trusts, which had exerted a virtual stranglehold on the American economy for decades. Previously, presidents of both parties—but especially Republicans—had been reluctant to intervene too directly in the running of the economy. The prevailing orthodoxy held that the American system of free enterprise was largely self-correcting and should, wherever possible, be left alone by the federal government. But Roosevelt challenged conventional wisdom, as his fifth cousin was to do almost thirty years later, and used the power of his office to reform some of the worst excesses of capitalism, such as child labor and the production of adulterated food and medicine.

The Presidency during the Gilded Age was largely made up of "caretaker" presidencies, where elected Congressmen and the President kept their hands out of economic interests and activities for the most part.  This was called a "laissez-faire" economy, where there was little regulation and business was extremely powerful.

Once Teddy Roosevelt inherited the office from a slain William McKinley, he changed the nature of the Presidency to an agent of social and environmental progress, and as a regulator of that same big business to level the competitive playing field, and to give consumers some measure of protection from the most dangerous products and working conditions.  With a few exceptions (the 1920s Presidents, for example) it's been that way ever since.

In general, the presidency as an office came to be much more important during the Progressive Era than it had been before.

In the late 1800s, the Presidency was very weak.  Presidents did not exert themselves very much to try to affect policy.  Congress pretty much ran the country.

Starting with Theodore Roosevelt, this changed.  TR was the one who described the office as a "bully pulpit."  "Bully" meant "really good."  He believed the office gave him the chance to really push the people and Congress towards various ideas and policies.

Because of this, and because the Progressives wanted government to enact a lot of reforms, the Presidency got much stronger during this time.