If I might add something.
The problem of public servant corruption started long ago in the West.
The concept of honorable service to the community was never embraced in the West in the manner it was in the far east.
Because of the classicism inherent in the West's social doctrine, no honor nor special merit was given to those 'functionaries' who performed
services for the public good. Often these 'careers' were a matter of forced servitude or 'lower' class employment.
Autocracy and Feudalism, or geneologically-contrived Tribal succession serve to fracture social merit into distinct categories. As society evolved
the need for a more sophisticated model of internal governance allowed for the elevation of prestige and social perks which were available to the
public servant. Eventually, as the proportion of serfs to lords became more skewed it became inevitable that sustainable governance required
ministerial duties to be delegated outside the upper class circles.
In part, because of the industrialization of the financial sector, money became the superlative tool for enticing loyalty, service, and even reward of
ministerial public servants, without the need for diluting the aristocratic or tribal leadership's concentration of power.
From that point forward, we became slaves to money. It has driven us from meritocratic, egalitarianism to debt-serfdom. All because money by it's
own nature, knows no loyalty, nor limits its movement through restricted circles as any non-owner desires. "The spice must flow."
Corruption began there. The notion that 'fractional reserve lending' is a reasonable model upon which to allow bankers to function is the ultimate
'free ride'. And make no mistake about it, the bankers knew then, and now, that without it their illusion of control collapses. They bought that
power, because they conspired with industrialists in War and Education to ensure that the model be rendered 'unchallengeable' and virtually
'infallible.'
Some might say they use subterfuge and criminal methods to ensure they received that irrevocable boon from Royalty and Governments around the world.
Perhaps we will never know, but it does seem a reasonable supposition considering the history we are aware of.
Ultimately, they inserted themselves as the middle-men of all international affairs, their supreme goal was to dominate ALL commerce, and so they
have. America had yet to exists as a concept before all this had already been accomplished.
The "Central" banking practice was repeatedly forced down our young nations throat several times, even by some of our founding fathers, who seemed
ill-disposed to fight it. Each time we vomited the poison out, and ended up in one war or another... each time people proposing that we 'borrow'
money to win the wars.
Our Presidents resisted, they had seen, some first hand, what happens to nations who 'borrow' for war. And much to the dismay of early America's
enemies, she was not 'an easy mark'. We kept winning our conflicts, despite lack of 'international' funding.
I'm sorry for the lengthy reply, but the point of this all is that the question you ask needs a very specific answer, one that includes a foundation
that can't be given to you with a simple date, or name.
American corruption existed from the start, because corruption has no nationality. It would be more direct to answer that corruption 'took hold' in
America the day the political parties abandoned the principles of patriotism and loyalty to American values, over winning elections.
It became about winning. Which is easier when you know how to 'sell' your party to the people and the party sponsors. As soon as the psychology of
'selling' was introduced to the political party machinery, we lost them.
In the end our political parties sold out to the same buyer, leading us to the now clearly failed make-believe 'two-party' facade that is in fact a
'one party' system.
Corruption, like anything else in human behavior, is a matter of degree.
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If your question had a more specific focus, like the economy or banking, or the military industrial complex, or the legacy and heritage of the robber
barons, the answer would take a different form.
I will go with the Jekyll Island - Federal Reserve Act. It was then that the bank cartel was able to establish their control of the United States
economy, and with that, The policies of her Federal Government (like the IRS). So the time I would give would be 1913, on Woodrow Wilson's watch.
But don't be too hard on Woody. He was merely a well-spoken, elite and charismatic academician, propped up by banker monies to win the election
(sound familiar?) He did what he was advised to do. Afterward, he saw the abuse to which he had been subjected and accepted that it had been a
tragic mistake.
But by that point the new private bank, which adopted the name "Federal Reserve Bank" had acquired a total monopoly on money production, and lending
rate control, with no oversight and no legal liability to perform, as well as iron-clad immunity from redress.
Depressing, huh?