Railways were first introduced to India in 1853 when a line was constructed from Mumbai to Thane covering a distance of 34 km. Since then Indian Railways have grown into a vast network. By 1947, the year of India's independence , there were forty-two rail systems. In 1951 the systems were nationalised as one unit, becoming one of the largest networks in the world.  At present it is one of the largest and busiest rail networks in the world, transporting over 18 million passengers and more than 2 million tonnes of freight daily. It is the world's largest employer, with more than 1.4 million employees. The railways traverse the length and breadth of the country covering 7,137 stations over a total route length of more than 66,030 kilometres.