Construction is set to commence in earnest on one of the single biggest projects in the Boston area: A 4.5 million-square-foot development within the 45-acre NorthPoint site where Cambridge, Somerville, and Boston converge.

San Francisco-based developer DivcoWest—which bought the acreage, the largest buildable parcel in Cambridge, in 2015—has started construction on one building there and will officially break ground on the 430,000-square-foot science-and-tech hub on October 19. (The developer is billing the project as a direct competitor of an increasingly expensive Kendall Square.)

And DivcoWest’s president of development told the Globe’s Tim Logan that the company is ready to move forward on the rest of the project.

When it’s all built out, what DivcoWest is now calling Cambridge Crossing—or CX for short—will include 2.1 million square feet of tech and office space in five buildings and as many as 2,400 condos and apartments (as well as 2,500 residences already in the footprint).

There will also be 11 acres of open space, and the project will be near the relocated Lechmere stop that’s part of the Green Line extension.

The plans are currently moving through the approval processes in Cambridge, Somerville, and Boston, so a definitive timeline is not yet set.

But, given its location and the residential and commercial real estate markets (at least currently), DivcoWest should find plenty of demand for the new offices and residences. Stay tuned.