Chemistry is engaged with a subject that is not static but evolving in time, in chemical space, namely, the collection of all substances and reactions reported over time. If we accept that premise, we can identify the path dependencies and self-reinforcing mechanisms that determined its current space and selected it across historical alternatives. In particular, data analysis allows us to identify two crucial turning points. One was the introduction of structural theory in 1860, the other a technological shift around 1980.