John Mitchell, Nixon's former Attorney General--ironic, since the AG is the top law enforcement official.
I don't think Mitchell went to prison.
That's incorrect. Mitchell, Haldeman, Dean, Ehrlichman, and Colson were among the highest ranking Nixon administration officials who went to prison.
Going back to the original question, I think Jimmy Hoffa and John Gotti would be considered powerful Americans who served time. Bernie Madoff also fits that description - he helped create the NASDAQ.
