Government was different in the 19th Century, but not as starkly different as some people believe. The 20th Century was the Progressive Era. Foreign policy went from staying out of European quarrels to policing the world whether the world desired policing or not. Unchecked government intervention became the rule.
Teddy Roosevelt and Woodrow Wilson were the mothers of all pernicious 20th Century policy. Roosevelt was a psychopathic proto-fascist. Wilson was more a humorless Lenin-like person. Wilson plunged the nation into unnecessary WWI, busting up four empires, and guaranteeing that more war would happen.
FDR was a full-fledged Wilsonian who prolonged the depression and WWII. The pygmy Truman had a domestically corrupt administration and a failed foreign policy. Eisenhower delivered a quieter time. The modern welfare state was put in place in the 60s and 70s.
Why did we move from limited government to galloping statism? Are we really better off having government experts running things? Men like John Dewey helped push us into collectivism. Great uncertainty for business was created by new federal agencies. Unfounded fears about running out of simple resources like timber served to expand governmental control. Conservationists have never understood the concept of value versus economic behavior.
Lecture 4 of 10 from Robert Higgs' Crisis and Liberty: The Expansion of Government Power in American History.