The City and South London Railway (C&SLR) was the first deep-level underground "tube" railway in the world, and the first major railway to use electric traction. The railway was originally intended for cable-hauled trains, but owing to the bankruptcy of the cable contractor during construction, a system of electric traction using electric locomotives; an experimental technology at the time; was chosen instead.
When opened in 1890, the line had six stations and ran for 3.2 miles (5.1 km) in a pair of tunnels between the City of London and Stockwell, passing under the River Thames. The diameter of the tunnels restricted the size of the trains, and the small carriages with their high-backed seating were nicknamed padded cells. The railway was extended several times north and south, eventually serving 22 stations over a distance of 13.5 miles (21.7 km) from Camden Town in north London to Morden in Surrey.
Although the C&SLR was well used, low ticket prices and the construction cost of the extensions placed a strain on the company's finances. In 1913, the C&SLR became part of the Underground Group of railways and, in the 1920s, it underwent major reconstruction works before its merger with another of the Group's railways, the Charing Cross, Euston & Hampstead Railway, forming a single London Underground line called the Northern Line. In 1933, the C&SLR and the rest of the Underground Group was taken into public ownership. Today, its tunnels and stations form the Bank branch from Camden Town to Kennington and the southern leg of the line from Kennington to Morden.
The railway was opened officially by Edward, Prince of Wales (later Edward VII) on 4 November 1890.