Yes, there's some truth in your arguments, but also fundamental flaws and those begin with your efforts to impose your own very high moral standards on people who do not, or did not, recognize your standards as legitimate.
It's a flaw you well understand regarding, for example, our slaveholding Founding Fathers, but when you're own favorite ax needs sharpening, you're OK with using historical congress-critters as whetstones.
So, your basic root problem here is that Congress itself, not DiogenesLamp, defines by law what is, or is not, "corrupt" and so far as I know, Nancy Pelosi never once wrote a law which made her own wealth-grabbing activities immoral or illegal.
And if you don't believe me on this, then go and ask her yourself.
As for when did your definition of "corruption" begin in Congress, I'd naturally assume it began in some form on or around Day One, in 1789.
Why would you expect anything different?
The core of the dispute between North and South was whether or not the nation should embrace the Hamiltonian view of Government, or the Jeffersonian view of government.
The Hamiltonian philosophy viewed government as a tool meant to increase the wealth and prosperity of the nation. It favored activism in government, which is the very opposite of the Jeffersonian view of Laissez Faire government.
A large, activist government that creates policy on the basis of what will make industry prosperous and wealthy will inevitably evolve to be the tool of that industry, which will quickly learn that by *CONTROLLING* that government, they can use laws and policies to further increase their own wealth and power.
These are the seeds that will evolve into Fascism, which is the collusion between government and corporations to milk the populace to the maximum extent possible.
A small government is much harder to twist into a money making enterprise. When the government is small, and only does necessary things, there is not that much graft that can be gotten from it.
So given the chief architect of activism in government (Hamilton) began serving in 1789, perhaps you have a point when you say it goes back that far, though I think it took a couple of decades for it to really get entrenched.
Interestingly enough, I have recently been engaged in a conversation relating to this very point we are discussing now, on another thread.
"The Fop" has put forth some ideas that I had never considered before, and I find them intriguing. I have yet to notice any inconsistencies between the theory he's put forth, and my own understanding of past history.
Maybe you will find these ideas interesting too.
https://freerepublic.com/focus/news/4260158/posts?page=48#48