For those of you who happen to be curious about the history of impeachment, UGA's Peter Hoffer (history) is the expert, according to Cass Sunstein:

Here’s an excerpt:
NYT, October 31

"This week, Harvard University Press released Cass R. Sunstein’s latest book, “Impeachment: A Citizen’s Guide.” The timing is fortuitous. Although the charges filed by Robert S. Mueller III, the special counsel, did not implicate the president, the subject of impeachment is on peoples’ minds. We asked Mr. Sunstein, a professor at Harvard Law School, to recommend books that might help readers understand the history and process of charging a public official with misconduct.

"Despite its importance, impeachment is a challenging and arcane subject — the Finnegans Wake of constitutional law. Fortunately, there are some terrific books on the topic, helping to guide the perplexed.

"The most revelatory, I think, is “Impeachment in America, 1635-1805,” by Peter Charles Hoffer and N.E.H. Hull. The Declaration of Independence was ratified in 1776 and the United States Constitution in 1788. Who knew that in the colonies, impeachment had a history 140 years before the American Revolution started?

"Hoffer and Hull demonstrate that our nation developed a homegrown, all-American framework for impeaching high-level officials. By the middle of the 18th century, we converged on a republican understanding of impeachment, by which the colonists had the temerity, and the guts, to impeach officials