Twenty-six of England's rarest and best-preserved railway signal boxes, including those at Lostwithiel, Par and Totnes have been given Grade II-listed status.
The list, announced by the Department for Culture, Media and Sport, includes signal boxes dating from late-Victorian times.
In the 1940s, there were as many as 10,000 signal boxes but today fewer than 500 are in use by Network Rail (NR), which has joined English Heritage in seeking out the best examples of historic boxes.
Heritage Minister Ed Vaizey said: "Our interest in everything to do with trains and railways - and the 'golden age' of steam in particular - is one of our most endearing and enduring national preoccupations.
"Signal boxes are a big part of this, and so I am very pleased indeed to be able to list these lovely examples of the type. It is greatly to Network Rail's credit that they have worked so constructively with English Heritage to bring this project to such a successful outcome."
John Minnis, senior investigator at English Heritage, said: "These are very special buildings, at one time a familiar sight on our railway system. Today's listings will ensure that many of these highly distinctive designs, which were full of character, are protected for years to come, providing a window into how railways were operated in the past."
NR is decommissioning many mechanical signal boxes to consolidate signalling into 12 regional centres, as part of a 30-year plan to modernise the system and provide a better-value railway for Britain.
NR's head of community rail Jerry Swift said: "Our operating strategy would see a marked acceleration in the number of signal boxes decommissioned each year, so it is vital that we have plans in place to deal with that sensitively and sustainably."