The Board of Aldermen voted Monday night in unanimous support of the zoning changes and development agreement necessary for New Haven’s Downtown Crossing to move forward — paving the way for the largest downtown development project in generations.

The $135 million Downtown Crossing project will replace sections of Route 34 with urban boulevards and reclaim 11 acres of land in the cleared space. By approving the zoning changes, aldermen have permitted that the new land be converted into a mixed-use business district. The development agreement will transfer 2.4 acres of this land to real estate developer Carter Winstanley, who plans to erect a 10-story, 225,000-square-foot medical office tower on the 100 College St. site.

“Since the 2008 recession, no city in Connecticut and few in the Northeast have matched New Haven’s population and job growth,” Mayor John DeStefano Jr. said in a press release. “Tonight’s vote assures that New Haven will continue on that trajectory for years to come as the Downtown Crossing project brings thousands of new jobs and millions of dollars in economic development activity to the City.”

Elected officials, business leaders and community advocates plan to celebrate the historic vote and discuss the project’s path ahead at a press conference Tuesday morning. The conference will be held atop the Air Rights Garage, which overlooks the Downtown Crossing site, and DeStefano will be joined by State Sen. Martin Looney and U.S. Richard Blumenthal.

Gov. Dannel Malloy announced in June that multinational drug company Alexion Pharmaceuticals will relocate its headquarters to 100 College St. — becoming the central tenant of the new development. Alexion plans to move 350 of its current employees to New Haven and make an additional 200 to 300 new hires at the facility by 2017.