Site prep has begun for one of the Seaport’s largest and most-anticipated projects, and its developer is promising more to come.

Cottonwood Management Group, the developer of the M1M2 parcel in Seaport Square, has opened a regional office at 101 Seaport Blvd., which the company is hoping to use as a launching pad for more projects on the East Coast.

“This is a major milestone for our team, to open our new office space and to start pre-construction in the same month,” Cottonwood CEO Alexander Shing said. “M1M2 is Cottonwood’s first Boston project to break ground, and we look forward to expanding in Boston along with our other activities on the East Coast.”

The just-over-1M SF project includes a two-story, 125K SF retail base managed by WS Development. More than 730 residential units will rise above in a trio of towers: two for luxury condos and one for luxury condos, apartments and micro-units.

M1M2 will close the remaining Seaport Boulevard gap between Pembroke Real Estate’s Seaport Place and Skanska’s oval-shaped 121 Seaport Blvd., currently under construction. The project will officially break ground in May and is expected to finish in phases from late 2019 into early 2020.

CORRECTION, Mar. 24, 10:27 A.M. ET: Of the three towers in the M1M2 development, two will be luxury condominiums while the other is planned for a mix of condos, apartments and micro-units. A previous version of this story mischaracterized the third tower's unit mix. This story has been updated.