Sunday is May Day, and organizers and activists across the United States are planning celebrations to mark the 10th anniversary of the massive May Day marches of 2006. That year, more than 1.5 million people took to the streets to support workers’ and immigrant rights. It was one of the largest days of protest in the country’s history. Now we look at a new book by historian Peter Linebaugh entitled "The Incomplete, True, Authentic, and Wonderful History of May Day." Linebaugh is the author of many books, including "The Many-Headed Hydra" and "The Magna Carta Manifesto." Historian Robin D. G. Kelley has said of Linebaugh: "There is not a more important historian living today. Period."