[NOTE: This is a holiday repost of one of my earliest comments on writing biography. Happy New Year.]

This photograph shows Cornelius Vanderbilt, seated on the right with crossed legs and top hat, on the veranda of the Congress Hall hotel in Saratoga Springs in the 1870s. I like this image. It nicely illustrates life in Saratoga, the most famous resort town of the nineteenth century. It also shows what a celebrity Vanderbilt was.
In broader terms, it raises an essential question for the biographer: Who are all those other guys?
Secondary characters are as important to a biography as they are to a novel, but they are often overlooked and underused. Over the course of years of research and writing, the biographer can begin to grow a bit Ahab-like, ignoring all the other whales in the ocean. And, of course, when we pick up a biography, we expect it to tell a specific individual's story, and we can grow frustrated when a book wanders off topic for too long.
Secondary characters, though, serve valuable purposes in both research and narrative. By digging into the lives of those who surround the main character, a biographer often discovers new dimensions of the primary subject, uncovering fresh sources and facts. To take just one example from my study of Vanderbilt, I dug into the life of his second son, Corneil (as Cornelius Jeremiah was called). Epileptic and addicted to gambling, Corneil might not seem like a worthwhile target for research; in fact, he was a prolific letter-writer whose correspondence dwelled on his family troubles. His very weaknesses made him the perfect light for illuminating the long-overlooked emotional life of his father, who struggled with contradictory feelings for Corneil.
Secondary characters are invaluable in crafting a narrative as well. For one thing, subplots and diversions from the main narrative line enrich a biography, just as they do in a novel, offering relief from a monotonous focus on just one character. Zeroing in on secondary characters also illuminates how events take place through the intersection of the intentions of multiple individuals, the collision of sometimes conflicting agendas. By following the purposes and actions of those who surround the main character, a biographer offers a fuller understanding of how that life unfolded—and can provide some dramatic tension.
Lest I sound like I believe I am a great craftsman in the use of secondary characters, I should note that I had little choice. Vanderbilt left no collection of papers. The letters by and about him are scattered in multiple archives, and do not amount to the kind of treasure trove that draws biographers back to a well-documented subject again and again. In pursuit of more information, I was forced to delve into the lives of those who surrounded him. Generally speaking, necessity proved to be a virtue—though only after assiduous editing. I got carried away with my fascination with some minor characters, and had to cut a great deal from the manuscript. In general, however, my advice is to keep asking who those other guys are; the answers are bound to be illuminating.

