The Google n-gram viewer has become a common starting point for historical analysis of word use. But it only tells us about individual words, with no indication of their context or meaning. Several months ago the Hathi Trust Research Center released a dataset of page-level word counts extracted from 250,000 out-of-copyright books. I’ve used it to build a word similarity tool that tracks word co-occurrence patterns from 1800 to 1923. In the default example we see that “lincoln” is a town in England until around 1859, when it becomes a politician. In this article I’ll describe how I made this tool, and what’s wrong with it.