Bowlers, Beavers and Holmes

Did your father, grandfather wear a hat? It used to be said "If you want to get ahead, get a hat." Look at films of street scenes from the early 1900s and everyone is wearing one.
Continuing to catch up with Gresham College lectures, Timothy Long, Curator of Fashion & Decorative Arts at the Museum of London, explores the history of the bowler hat. You can read the transcript, which is not complete, but I recommend taking the time to view the presentation which has interesting extra information. Both are at http://www.gresham.ac.uk/lectures-and-events/the-history-of-the-bowler-hat.
The earliest newspaper reference to a bowler hat that I could find was in The Times in 1856, a court case in Taunton "They had on their heads "bowler" hats fastened under the chin."

In the US, where they're known as the Derby hat, and Canada, mentions are from the 1880s. This ad from March 1883 is from the Ottawa Citizen.