⁌ ULY ⁍added a comment 5 years agohttps://books.google.com/ngrams/graph?content=worked+in+factories%2Cworked+at+factories&year_start=1800&year_end=2008&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cworked%20in%20factories%3B%2Cc0%3B.t1%3B%2Cworked%20at%20factories%3B%2Cc0