Together, the two companies proposed to construct a railroad between Montreal and Portland across the province of Quebec and the states of Vermont, New Hampshire, and Maine.

Construction resumed and reached the town of Northumberland, New Hampshire, on July 12, 1852, passing through the new Berlin station en route.

Meanwhile, the St. Lawrence & Atlantic built southeastward from Montreal, and the two companies had agreed on August 4, 1851, to join at the town of Island Pond, Vermont.

Meanwhile, the directors had negotiated the joining of the two railroads between Portland and Montreal into the Grand Trunk Railway Company of Canada, which they accomplished through a 999-year lease dated August 5, 1853, but retroactive to July 1, 1853, roughly three months after completion of the through railway.

Thus Berlin, New Hampshire, took its place on the map of railroad stations in the United States, for the first several months as part of the Atlantic & St. Lawrence and thereafter as a stop on the Grand Trunk Railway.