Here is a short, transitioning from the Wikipedia introduction of a previous post, to a closer look at the Steam Nation.

In the fiction, Manchuria is constructed and ruled by the Pure Land Motion Railroad Corporation. You could say that the Pure Land Motion RR is literally embodied here, but in fact that is just the narrator, narrating in the center of the screen as the pictures tell the story. The Pure Land Motion RR came into being many years before, or ago, at a time when the Japanese started to  become expert in the construction of mobile cities. As part of the work of the Railroad, these eventually left Japan, and ended up on the Chinese mainland, in the new country of Manchuria. There is a problem, however, which is that  Manchuria is after the literal End of the World... ie that broken zone after the edge of the flat earth. Having traveled too far, the Pure Land Motion RR has fallen over this end of the earth, and falling, has arrived at Manchuria, which is more than a country, but in fact an entire planet in the sky.

In history, or the Wikipedia, or other books, Manchuria as a nation [of sorts] came into being directly from what was called the South Manchurian Railway Zone, an independent political entity which itself came into being after the Russo-Japanese War, and which in places wasn't much wider than the railroad that ran inside it, from the sea towards the center of the country. Thus, the railway was both the country and the border, in a certain sense.