Where can I find recorded speeches about working in factories during the first half of the 20th century?
You might contact The Center for Lowell History for some of their oral history materials. This might be of special relevance, since the City of Lowell, MA was literally built as the first site for large scale factory work in North America. The principal industry there from the 1830s was textile manufacturing, using the power of the Merrimack River’s natural head at the nearby falls. In the first half of the 20th century, subsequent waves of immigrants washed through Lowell, transforming the city from a New England culture, to one heavily influenced by the Irish, Greek, and Italian immigrants that came. The story of Lowell is also chronicled in a unique urban National Park, which also has some audio interviews, speeches by mill workers trying to organize at various times, and related materials.
