Going back even further than our previous 1927 Underground map, the map above shows the network as it was in 1907.
This map is printed on card with a dark green backing. 1907 is our estimated date for it, but it does feature both Hammersmith (Grove Road) and the Hammersmith & City service to Richmond which ended in December 1906. Whether this was simply a result of the map being printed before a decision had been made, or whether it dates it slightly earlier than we suspect is currently unclear.
Thanks to Martin for the map