The last Railway Series book written by Rev. W. Awdry was published in 1972.
That book was Tramway Engines, the 26th main volume in The Railway Series. It was published on 15 October 1972 and contains four stories: “Ghost Train,” “Woolly Bear,” “Mavis” and “Toby’s Tightrope.” The book focuses heavily on Thomas’s branch line and introduces Mavis, the headstrong diesel who works for the Ffarquhar Quarry Company.
Awdry had written the first 26 Railway Series books, beginning with The Three Railway Engines in 1945. After Tramway Engines, he retired from writing the main series because creating new stories had become increasingly difficult. Although he considered a 27th book, there was an 11-year gap before the series resumed.
A frequent mistake is to confuse the final Awdry book with the final Railway Series book overall. Christopher Awdry later continued the series, beginning with Really Useful Engines in 1983. Thus, 1972 is the correct date for the last book written by Wilbert Awdry, not the end of the entire publishing history.