^ If you go way back, they weren't "rain gutters". They were "eave troughs". The nomenclature changed somewhere along the way.
I had a hell of a time trying to figure out a patent number on an "eave trough holder" because I couldn't figure out what they were talking about. Finally figured out it was a device to hold up a "rain gutter".
I would not find it surprising at all to discover that cast iron was employed for that purpose, particularly at the end of the 19th century.