The great David McCullough discusses how his three books -- "The Great Bridge," "The Wright Brothers," and "The Path Between the Seas" -- represent an unofficial trilogy about the American spirit, ingenuity, engineering, and courage. History lessons like this right to your mailbox each month. Subscribe: http://bit.ly/1RUXzZQ | History in Five

David discusses his lifelong love of libraries and the vital role that librarians play in his research and writing. | David McCullough