(Musical break.) MR. WATTENBERG: Hello, I’m Ben Wattenberg. In his new and best-selling book, April 1865, author Jay Winik argues that the most critical month in American history was April 1865.

Arguably the nation's most famous assassin, John Wilkes Booth was an accomplished actor, southern sympathizer, and likely spy before shooting President Lincoln in April 1865. The ninth of 10 ...