Who Built the Railways?

Most railways in the world were built in the 19th century and so there wasn't much mechanization. There was some kind of steam portable steam engines as it were that helped dig things out but by and large they were dug out by hand tunnels were built by people kind of using explosives and the likes. It was quite dangerous you know land slips and an explosion would would kill people  it was vastly labor intensive so it they were kind of particularly in the UK for exampleThere were bunches of navis they were called navis because they've also built the canals and there were huge groups of people set up in tents and and temporary hats to build a few miles of railway.