The county of Peebles with all the burghs situated therein, and the Gala Water and Lasswade County Districts of Midlothian (except that part of the latter district which is included in the Northern Division) with all burghs situated therein except the burghs of Leith and Musselburgh.
Until 1918 the area of the constituency was, at least nominally, partly within the Peebles and Selkirk constituency and partly within the Midlothian constituency.
General Election 1939–40:
Another General Election was required to take place before the end of 1940. The political parties had been making preparations for an election to take place and by the Autumn of 1939, the following candidates had been selected;