The City and South London Railway was the first deep-level underground "tube" railway in the world, and the first major railway to use electric traction. Originally intended for cable-hauled trains, the collapse of the cable contractor while the railway was under construction forced a change to electric traction, an experimental technology at the time, before the line opened. When opened in 1890, it 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. 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 and Kennington to Morden section of the London Underground's Northern Line. (Full article...)