Conversation so far:
What does Robert Owen have to do with the New Lanark textile mill?
In July 1799 Owen and his partners bought the New Lanark mill from David Dale, and Owen became the New Lanark mill's manager in January 1800.

Question: When did he stop being a manager of the textile mill?
Self-contained rewrite: When did Robert Owen stop being the manager of the Lanark textile mill?