Nathaniel Philbrick, author, Bunker Hill: A City, a Siege, a Revolution

In 1675, the considerable promise of the First Thanksgiving in 1621 was destroyed by a devastating Native American–English clash. On a per capita basis, King Philip’s War was the bloodiest conflict ever fought on American soil.

Peter Segal, director, Anger Management, 50 First Dates, and Grudge Match (out December 25)

Definitely 1848, the year gold was discovered at Sutter’s Mill. Until then, you could find a nice piece of land in California, pitch your tent, and call it home. The housing market here has been a living hell ever since.

Margaret MacMillan, warden, St. Antony’s College, University of Oxford

Until the end of July 1914, Europe was rich, prosperous and peaceful. By that December, hundreds of thousands of men lay dead across the Continent and, although the world did not know it, Europe faced another four years of a conflict that would cast a long and poisonous shadow over the future.

Mark Kurlansky, author, Ready for a Brand New Beat: How "Dancing in the Street" Became the Anthem for a Changing America

There’s a direct connection between 1914—which saw the outbreak of World War I and the initial embrace of modern warfare—and World War II, the Korean War, Vietnam, Iraq, and even today’s drones.

John Barry, author, The Great Influenza: The Story of the Deadliest Pandemic in History

The year 1918 saw not only the butchery of World War I but a worldwide influenza pandemic. Credible estimates of the death toll range from nearly 2 percent to well over 5 percent of the entire world population. It’s possible that influenza killed more people in September, October, and November of 1918 than AIDS has killed in all the years since it entered the human population.

Lisa Randall, professor of physics, Harvard

Despite being the year after World War I ended, 1919 wasn’t so great. It planted the seeds for World War II as well as for many of the Middle East problems we face today. Plus, between 1918 and 1920, influenza killed a significant fraction of the world’s population.

Molly Crosby, author, The American Plague: The Untold Story of Yellow Fever, the Epidemic That Shaped Our History

The year 1918, when man’s technological advances culminated in one of the deadliest conflicts in world history. Then, in an ominous reminder of the real enemy, a strain of flu killed as many as 50 million people.

Erik Larson, author, In the Garden of Beasts: Love, Terror, and an American Family in Hitler’s Berlin

The first 10 months of 1918 were consumed by world war, and even after the war ended, than the Spanish flu epidemic continued.

Niall Ferguson, professor of history, Harvard

The high tide of the Axis powers—and the most lethal year of the Holocaust—came in 1942, as the Germans ran amok in the Soviet Union and the Japanese smashed the Western empires in Asia. The same year, the tide turned in favor of the Allies at Stalingrad, Guadalcanal, and El Alamein, but think how much longer the war still had to go! What a bloody awful year.