How the Transcontinental railroad forever changed the US

"You can almost feel the pain it took," said Roland Hsu, standing inside the train tunnels along Donner Summit in California's Sierra Nevada mountains.

Jagged and bumpy, the walls of the tunnel hardly resemble underpasses made by modern-day machinery. Instead, in the 1860s, teams of Chinese labourers blasted through the granite and painstakingly hand-chiselled 15 shafts through the Sierra Nevada so that the first transcontinental railroad could whisk passengers 1,800 miles from Sacramento, California, to Omaha, Nebraska, cutting travel times from six months to just six days and forever transforming the nation.

Read the whole story at BBC.