When the line between Durban and Pietermaritzburg in Natal was the first South African line to be electrified, the South African Railways ordered the first 78 units of the four-axle Class 1E, which at the time was the largest order for an electric locomotive worldwide. Due to the large numbers, the locomotives were partly built in Switzerland by SLM and in England by Metropolitan-Vickers. They were modern engines with two two-axle bogies with all axles powered independently. For the first time, a DC voltage of 3,000 volts was used, which is why the bogies were connected in series and the motors were therefore operated with 1,500 volts. The locomotives were intended for all types of trains and could be used in multiple.

From the beginning the plan was to use between one and three locomotives, depending on the weight, route profile and required speed of the trains. The ultimately 172 pieces in seven series came mainly from the manufacturers mentioned. In 1938 the sixth series of 20 locomotives from Werkspoor in the Netherlands followed, and in 1944 the last ten of the seventh series from Robert Stephenson and Hawthorns. Due to the circumstances of the war, the latter were delivered in parts and assembled in South Africa. The 1E had a very long life, lasting until about 1990. As early as 1936, two units were equipped with a different transmission for 90 km/h or 56 mph, but they remained prototypes. Some locomotives have been converted to shunting locomotives over time and designated as Class 1ES. A total mileage of more than five million miles is stated for some engines.