Network Analysis Applied to History

A study of Historic Figures in the American Revolution

If we could draw a map of George Washington's social network, what would it look like? How many nodes would it contain and who would be considered a friend, a colleague or an adversary? How might we even determine who was in the same network as George Washington? Unfortunately it's not as simple as John Adams or Alexander Hamilton sending friend requests on Facebook.

We can take a stab at identifying the nodes to which he is connected by examining the tremendous amount of correspondence written to and from George Washington. Additionally we can determine which of the people connected to George Washington are connected to one another in order to gain a sense of the larger network to which they all belonged. To do this we first can look for additional letters written by the 'alter' connections to one another. Second we can look for references by alter connections to one another within their letters. For example when reading the letters from the Marquis de Lafayette to George Washington it is obvious they had a very close friendship, however flatteringly he spoke of the Marquis he was not always so kind when speaking of General Horatio Gates. The more subtle hints of friendship between correspondents in the 18th century also exist. Most letters start with 'Sir' and end with 'your obedient servant etc' or a similar variation. When letters open with something like 'My Dear Laurens', as the Marquis was prone to address Washington's Aid de Camp John Laurens, then it becomes safer to assume that they were more than just co-workers. Occasionally correspondents refer to others in their letters in similar terms - 'our good friend', 'my friend' etc which gives the reader a glimpse of a potential network as is the case when John Jay wrote Robert Livingston and mentioned their mutual friend Gouverneur Morris.

Tracking what a few hundred correspondents say of one another through several thousand letters is no easy task but isn't as tedious as it may sound at first. The first step is establishing a matrix of all correspondents. For the purposes of this study I used four volumes of roughly 1000 letters written to General Washington as well as several more volumes written by Washington. As other nodes in the network became apparent I found volumes of letters for them as well - John Jay, Alexander Hamilton, Aaron Burr and Timothy Pickering to name just a few. Anyone who wrote a letter becomes a node in the matrix. Each node has several potential relationship types with every other node in the matrix. How exactly the multitude of potential human relationships can be distilled into a meaningful set of terms is open for debate. I settled on XFN (Extensible Friend Network) a micro format aimed at finite set relationships ranging from professional to friendships, family and more. Each letter contains potential information about points in the matrix. Each time a node (the ego) mentions another node (the alter) an XFN tag is wrapped around the alters title with the appropriate relationship information. For example if John Jay mentions his friend and colleague Gouverneur Morris in a letter as 'our friend Morris' than the surname 'Morris' has a simple html anchor tag added with the XFN keywords 'colleague friend'. (More on XFN markup). Determining and inserting the relationship markup is an iterative process and largely manual at first, requiring some normalization, but can be automated after several letters have been processed for a given node.

But leaving the relationships information embedded in the documents is only half the job. The next step is programmatically harvesting the XFN information from thousands of letters and feeding it into a social network ruleset. The ruleset will help answer interesting questions like when can a group of friends that are also colleagues, and perhaps kin, be considered a clique or some other form of a network? Part of the rulesets job is determining how close one individual is to another - otherwise known as their proximity. Learn more about how the strength of relationship ties is determined.

Lastly, historians get to explore interesting questions such as - based on how a person is situated within their network what opportunities and constraints they did have at the time and how did this influence their decision making?

Learn about some basic social network analysis terms.