Why not go back to Washington' time and take a look at the companies selling government lands? Take a look at the banks financing those sales.
Greed is about as constant as an atomic clock.
Regarding the specifics of corruption sure it existed before 1861 but it was checked to a degree by partisanship, regionalism and sometimes even a respect for constitutional law. Lincoln and the GOP's success established corporate welfare, bribery and graft as official policy, all at the expense of the general public. Conservatives tend to blame all of today's ills on FDR and LBJ. The point is we were in trouble long before them.