The first London Underground line opened in 1863. It was the Metropolitan Railway, which began public services on 10 January 1863 between Paddington and Farringdon Street.
The railway was built mainly by the cut-and-cover method: workers excavated a trench, constructed the tracks and tunnel, then covered it again. Its purpose was to connect London's major railway termini with the City, reducing severe traffic congestion on the streets. The original route was about 3.75 miles long and had seven stations.
The trains were hauled by steam locomotives and used gas-lit wooden carriages, so the early journey was smoky and uncomfortable by modern standards. Nevertheless, the line was an immediate success, carrying about 38,000 passengers on its opening day.
A common mix-up is confusing the Underground's first opening with later electric Tube lines. Deep-level electric railways came decades afterward; 1863 refers to the opening of London's first underground passenger railway, the Metropolitan Railway.