The Enlightenment idea of historical moral progress asserts that civil societies become more moral over time. This is often understood as an expanding moral circle and is argued to be tightly linked with language use, with some suggesting that shifts in how we express concern for others can be considered an important indicator of moral progress. Our research explores these notions by examining historical trends in natural language use during the 19th and 20th centuries. We found that the associations between words denoting moral concern and words referring to people, animals, and the environment grew stronger over time. The findings support widely-held views about the nature of moral progress by showing that language has changed in a way that reflects greater concern for others.