For half a century, Zinn, a WWII veteran, was a thorn in the side of orthodox historians, taking an aggressively sharp eye to the "underside" of American history, unpacking this nation's foundation mythologies to reveal genocide, corruption and hundreds of years of brutality and iniquity. Not surprisingly, Zinn had his fair share of run-ins with institutional authorities, getting fired from his first job at Spelman (an all-black women's college, where he taught Alice Walker) for criticizing their non-participation in the civil rights movement, and having frequent acrimonious clashes with Boston University President Jon Silber, his boss for many years.
Zinn's most famous work, 1980's A People's History of the United States, was tonic to millions of Americans sick of the patriotic bromides forced on them from cradle to grave; not the least of the book's accomplishments was inspiring Bruce Springsteen to write and record Nebraska, as fine and resonant an artifact of the American experience as there is.
Ultimately, Zinn wasn't positing some wholly "true" alternate history of this country, but was, with his work, demonstrating the slippery, multifarious aspect of history, warning us to guard against the easy acceptance of subjective readings, lest they drift into received orthodoxy. As he said himself:
There’s no such thing as a whole story; every story is incomplete. My idea was the orthodox viewpoint has already been done a thousand times.
To which I say amen, and RIP.