The Treeline Cos., a privately held Garden City business that owns more than 1.5 million square feet of office space in the tri-state area, has paid $46million to acquire a prime, 207,000-square-foot building at 990 Stewart Ave. in Garden City, a Treeline executive said Friday.

The purchase is "strategically critical," said Howard Schor, vice president for strategic planning and operations at the family-run company. "What we're looking to do is build up sectors of strength," he said, and the Atria East, as the Stewart Avenue building is known, is "within a small radius" of numerous other Treeline holdings, as well as the commercial and legal centers of Nassau County.

The politically connected law firm Meyer, Suozzi, English & Klein P.C. is headquartered in the building, which Schor said was already 100 percent leased by previous owner Heritage Management. He said his company's strong presence in the area, not far from the county offices and county and state court complexes, has helped Treeline secure "seven or eight of Long Island's top law firms" as tenants.

Officials of Heritage Management Co. of Ridgewood, N.J., which said in a news release that it bought the building in 2005 for $37 million, could not be reached for comment.

Michael Harris Spector, the building's architect and founding principal of the North Hills-based Spector Group architectural firm, said the "very simple and dignified" structure, part of a two-building complex, influenced much subsequent construction in the area. "It was the original role model for all that work done on Stewart Avenue, some of which is very good," Spector said. He said the building went up in the early 1980s.

Schor said the long-discussed and slow-moving redevelopment of the nearby "Nassau Hub" area surrounding Nassau Coliseum has increased the value of buildings in the area.