Kellen Funk and I are working on detecting how a New York legal code of civil procedure spread to most other jurisdictions in the United States. That Field Code and the other codes derived from it are the basis of modern American legal practice, so tracking the network and content of the borrowings reveals the structure of a significant part of American legal history.In response to an invitation from the Digital Humanities Working Group at George Mason, we wrote a **[working paper](http://lmullen.github.io/civil-procedure-codes/talks/dh-working-group/Funk-Mullen.Migration-Field-Code.working-paper.pdf)** that describes the current state of our research. In the paper we explain the historical problem to show why it is worth tracking how the Field Code spread. Then we give an overview of how we went about detecting which civil procedure codes were similar to one another, after which we give a few sample visualizations to show how we went about learning from those similarities. And finally we wrap up with a summary of what we think our project tells us about the history of nineteenth-century American law. We are working on an article, which will be structured rather differently with a fuller statement of our argument and many more visualizations, but in the meantime [the working paper](http://lmullen.github.io/civil-procedure-codes/talks/dh-working-group/Funk-Mullen.Migration-Field-Code.working-paper.pdf) gives a fairly succinct overview of the project and its argument. It may also be of interest for going into more detail as to how a historical data analysis project proceeds from problem to interpretation than we may be able to do in the article. We also have a [notebook](http://lmullen.github.io/civil-procedure-codes/) with more details about the project.