The world's first underground passenger train opened in London on January 10, 1863.

The first line was 3.75 miles long and connected Paddington to Farringdon Street. Workers used a method called cut-and-cover to build it. They dug a deep trench in the road, built brick walls and a roof, and then put the road back on top.On the first day, 38,000 people rode the train. By the end of the first year, 9.5 million people had used it. Charles Pearson, a city lawyer, pushed for the project to help stop overcrowding in London. At the time, London was the most crowded city in the world.The trains used steam engines that burned a fuel called coke. This created a lot of smoke inside the tunnels. Engineers had to build special vents and open-air sections so the steam and smoke could escape.The tunnels were made of millions of bricks and are still strong today. This success led to other cities building subways, including Budapest in 1896 and New York in 1904. Even without modern tools like GPS, the original tunnels were built with almost perfect accuracy.