When the constituency was created, it was defined to include three whole wards of the Metropolitan Borough of Southwark (St Mary's, St Paul's and Trinity) together with a small section of the St George's ward. This formed an area in two main parts linked by a narrow strip of land around Elephant and Castle. The southern section, between Kennington Park Road and Walworth Road, including the St Mary and St Paul wards, was almost entirely residential. It stretched to Kennington Park and to Avenue Road, being the southern boundary of the borough. Around the Elephant and Castle area the constituency included Newington Butts and the Metropolitan Tabernacle, but at its narrowest point it was only about 100 yards between the western boundary on Newington Causeway and the eastern boundary on the railway line through Elephant & Castle railway station.
North of Elephant and Castle, the constituency turned to the east and included a second area of Newington between New Kent Road and Newington Causeway in the Trinity ward. The southern boundary of this part of the constituency continued along New Kent Road to divide St George's ward along it and Tower Bridge Road up to the borough boundary with Bermondsey. The northern part of Trinity ward, north of Wickham Place, was not included. The constituency's last MP, future Chancellor Roy Jenkins, described it as "postage stamp-sized".