It is all too easy for successful writers to slide into a comfort zone and never want to leave it. Writing is such an iffy proposition, working from a formula isn’t just easier and safer for the psyche, it’s often the smartest business decision one can make--if it worked once, chances are pretty good it will work again.
The historian, author, PBS mainstay and owner of the most avuncular voice this side of Bob Ross , David McCullough has found his formula and shows no inclination to tinker with it. He's not out to stretch our minds or question the foundations of American Civilization. He's at heart a weaver of tales and he's exceedingly good at it.
McCullough understands better than any popular historian that it is the characters who make a story, and he has an uncommon talent for plucking little known figures from others' footnotes and showing how they reflect the larger historical themes of their day. While the figures we are familiar with, in this case Oliver Wendell Holmes , James Fenimore Cooper  and Charles Sumner  to name a few, are shown in McCullough's trademark slanted light to be disarmingly human. In the Greater Journey , we see Samuel F. B. Morse , the inventor of the telegraph, not as we know him from 5th Grade history, but as a talented and dedicated painter, who resists and ultimately comes to resent his world-changing invention. While the little known Elihu Washburne, a crony-appointment of U. S. Grant  to a diplomatic post in Paris, who was widely regarded as a flaming mediocrity turns out to be the Oskar Schindler  of the Franco-Prussian War  and its brutal aftermath, the Paris Commune .
And that is the gist of the McCullough Formula: the unknowns are shown to embody Big History, while the Big Names are jus' folks trying to make their way in confusing times. It's not E=MC2 but it works.
Other books by David McCullough
Brave Companions: Portraits in History 
The Great Bridge: The Epic Story of the Building of the Brooklyn Bridge 
In the Dark Streets Shineth: A 1941 Christmas Eve Story 
John Adams 
The Johnstown Flood 
Mornings on Horseback: The Story of an Extraordinary Family, A Vanished Way of Life, and the Unique Child Who Became Theodore Roosevelt 
The Path Between the Seas: The Creation of the Panama Canal, 1870 – 1914