Fairfax County’s board of supervisors Tuesday approved a townhouse development project in Reston that would mean demolishing a treasured building designed by acclaimed 20th Century architect Marcel Breuer.

The project to build 34 townhouses and an apartment building on the site currently occupied by the vacant American Press Institute building met with fierce resistance from preservation groups and some local residents.

The board voted unanimously to approve a proposal to rezone the land for higher-density housing and to demolish the 42-year-old API building after a lengthy public hearing Tuesday night where residents and preservation groups argued to save the only example of Breuer’s brutalist architectural style in Virginia.

“We’re motivated by a deep sense of history and a firm belief that the Breuer building should be adaptively reused,” said Carol Ann Riordan, a Reston resident and former API events planner who led a campaign to save the building. “Fairfax County is fortunate to have a building of such stature designed by a world-class architect. It deserves far more than a demolition permit.”

County officials said the building’s historical signficance had never been pointed out when a new comprehensive plan was being designed for Reston to accommodate higher-density housing near Metrorail’s Silver Line train route.

With no county funds available to save the site and no buyers expressing interest in restoring the building, several supervisors argued that they were bound to consider the merits of the development proposal alone, which falls in line with the county’s vision for Reston.

But the board convinced the project developer — Sekas Homes, Ltd. — to help preserve some aspects of the building, such as keeping the building’s furniture, and ordered county staff to document other potentially historically signicant properties in Reston.

“I recognize very much the historic importance of that building,” said Supervisor Catherine Hudgins (D-Hunter Mill), who represents the Reston area. She lamented that officials did not identify the historical significance of the building earlier.

“I think we all agree had that been done earlier,” Hudgins added, “we would have been having a very different discussion today.”