At the westernmost edge of northern Massachusetts, a great wall of rock rises up, as if to mark the boundary of the state and discourage anyone from traveling farther west. By the early nineteenth century, the Hoosac Mountain Range was proving to be a serious obstacle to the growth of the economy in the northern half of the state. Grain and other products were transported east from the rich farmlands of New York State, but the mountains forced traders to turn south down the Hudson River Valley. The products of northern textile, shoe, and paper factories could not flow across the mountains. In 1825 the legislature decided to commission a survey of the range in hopes of finding a passable route through it. The legislators had in mind a canal, but the very year the survey was approved, the first American railroad began operation. Plans for a Hoosac canal were put on hold.

In the next 20 years, a rail line from Boston to Albany was built to serve the southern half of the state. The B&A railroad company charged exorbitant rates for towns in the north to connect to their route; as a result, most northern towns remained isolated from western trade. The industrial entrepreneurs of northern Massachusetts, such as paper manufacturer Alvah Crocker of Fitchburg, pushed hard for a northern rail route. These private investors eventually built rail lines that led to the Hoosac Range from the east and from the west. Still, the mountains stood in the way, cutting communities off from the lucrative trade routes of the Hudson River to the south and the Erie Canal to the west.

By the middle of the century, industrialist entrepreneurs and investors were determined to construct a railroad tunnel through the Hoosac Range. Engineers and surveyors enthusiastically supported the idea. One is said to have exclaimed, "It seems that Providence had marked out this route from the east to the west!" A doubter replied, "Perhaps so, but it is a pity that the finger of Providence hadn't been thrust through the Hoosac Mountain." The distance was short — only four and a half miles — but the tracks had to pass through solid rock.

The enthusiasts prevailed. Although it took several years for investors to raise the money, on March 16, 1853, ground was finally broken in Florida, Massachusetts, for the Hoosac Tunnel.

No project on this scale had ever been attempted anywhere in the world. Engineers made use of every available tool, and several devices were developed specifically for the project. Even so, boring through five miles of rock would take more than 20 years and cost nearly 200 lives.

The engineers had no choice but to experiment, and many of the experiments failed. In 1852, for example, a 70-ton steam-driven machine with a flat circular cutting head was used to drill a 24-foot hole — the full width of the tunnel — in one operation. The machine managed to bore 10 feet into the mountain and then died. The device remained stuck in place — for years, in fact — and engineers had to start the tunnel over again in a new location. The hole from this aborted start can still be found in the woods near the east end of the tunnel.

Progress was slow. Workers used hand tools to drill holes that were then filled with gunpowder and blasted. Even with crews drilling inward from both sides and outward in both directions from a central shaft in the middle of the mountain, the tunnel opening grew by only 60 feet a month. At that rate, engineers estimated, it would take well over a generation to complete. The pace was so slow, that critics referred to it as "The Great Bore."

In the 1860s, two innovations helped speed things up. One was a compressed-air power drill, invented by Charles Burleigh of Fitchburg. The other was tri-nitroglycerine. The Hoosac Tunnel workers were the first to put this powerful but extremely unstable explosive to industrial use.

Progress on the tunnel accelerated but at great human cost. Accidents and engineering failures claimed 196 lives during the two decades of construction. Most of those lost were Irish or Cornish miners who had come to western Massachusetts for jobs on the tunnel project. The work continued around the clock, with 750 men rotating through three eight-hour shifts.

The men who built the tunnel also built lives on the slopes of the Hoosac Range. Around each opening, there were clusters of huts for the workers and their families, schools, and churches. Beyond the huts were wooden buildings that housed the blacksmith and the machine shops, the air compressors and steam engines, and the building where the nitroglycerine was made. Known as the East Camp and the West Camp, these temporary towns were home to a generation of tunnel workers and their families.

On February 9, 1875, 24 years after construction began, the first train passed through the tunnel. The first freight train followed two months later, and in October 1875, the first passenger train used the tunnel on its way from Boston to Troy, New York.

The Hoosac Tunnel has been enlarged to accommodate modern trains. It is still the longest transportation tunnel east of the Rocky Mountains.