Slideshow: Boston, Vertex 'Top Off' Fan Pier Building

BOSTON — The structural framework of the country's largest privately funded development site, located in the heart of the Innovation District, is complete.

The commercial tower is the first of two buildings being constructed for Vertex Pharmaceuticals on the Fan Pier, a 21-acre site on the South Boston waterfront.

Mayor Thomas Menino joined executives from Vertex, members of the Iron Workers Union and Joseph Fallon — the CEO the Fallon Company, which is developing Fan Pier — for the "top off" celebration, in which the final beam of the structure was erected.

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