I think Dylan just read about Hattie Carroll's death in a newspaper. His brilliant song was a gut reaction, an instinctive emotional response to the awfulness of the situation - tho probably a little short on factual accuracy as newspaper reports often are.

My daughter was in Baltimore recently and I asked her to check out the hotel but seems like it was demolished in the 70s.

Any accurate biographical info on Hattie Carroll would be much appreciated.