When was the first subway in Beijing built?

The first subway in Beijing was built at 1969. This is a subway line with a length of 2 1.2km, connecting Beijing downtown and Beijing West Railway Station. This subway line uses light rail trains because the technology at that time was not enough to support a more advanced subway system. With the development of Beijing city and the progress of technology, the subway system has been continuously improved and expanded. At present, Beijing's subway system has become one of the largest in the world, with more than 20 subway lines and more than 400 stations.