Theodore Roosevelt 1901-1909, was known as a trust-buster, champion of the environment, consumers, and other reforms. TR is known for the Meat Inspection Act and the Labelling Act. His progressive platform expanded when he ran again for President as an independent Progressive candidate in 1912.
William Howard Taft 1909-1913 was Roosevelt's hand-picked successor. Although he busted more trusts than Roosevelt, Taft was more conservative. When he fired Gifford Pinchot, Roosevelt's appointment as the head of the US Forest Service, Roosevelt broke with Taft, and ran against him, splitting the Republican Party, thus giving the election to Woodrow Wilson.
Woodrow Wilson 1913-1921 was a Democrat and a Progressive. Unlike Roosevelt, Wilson did not believe in the concept of good trusts and bad trusts, and sought to regulate business more thoroughly. Wilson is credited with helping to create the Federal Reserve Board, and pushing through the Clayton Anti-Trust Act of 1914. During World War I, Wilson's administration took a more interventionist role in the economy. Unlike Roosevelt, Wilson was only luke-warm on the issue of women's suffrage. Wilson also supported the segregation of African-Americans who were employed by the Federal Government.