Boston broke ground on its subway in 1895, with workers digging the trench in sections. Horse-drawn carts carried away the dirt and rocks.

The city managed to keep its busiest thoroughfares open to traffic. Rather than eliminate street-level rail service, engineers took the extraordinary step of designing a detour of the tracks.

On March 4, 1897, the sparks from an above-ground streetcar and an undetected gas leak combined to create a horrific explosion. Ten people were killed.

To raise the grade of the Public Garden and the Common to accommodate the subway, an estimated 9,000 cubic yards of fill were needed for the former and 62,000 cubic yards for the latter.

It was bright enough to read underground. The air was clean enough to take in one long deep breath and not notice any difference from aboveground.

Streets became so overcrowded in Boston, and in New York, in the 1890s that subways were seen as the last, desperate act of relief for pedestrians and street trolleys.

During subway construction in Boston, it was vital to businesses that trolleys still run, so people could still shop downtown.

At the Park Street station, when the subway opened in 1897, the city bubbled with excitement.