BOSTON—Executives with development firm the Fallon Co. and a host of dignitaries, including Boston Mayor Martin J. Walsh, were on hand this morning for the groundbreaking of the 100 Northern Ave. office building at Fan Pier.

The 17-story, 515,000-square-foot office building is being built as a build-to-suit for Boston law firm Goodwin Procter. The law firm will occupy 375,000 square feet of space on 12 floors of the building and currently expects to complete its move to the building in the summer of 2016. The tower will be Goodwin's fifth office location in the city since the founding of Goodwin Procter in Boston in 1912.

“We're delighted to partner with The Fallon Company on the creation of our new home at Fan Pier and the further development of this vibrant and exciting neighborhood,” said Regina M. Pisa, chairman of Goodwin Procter. “Our move to the waterfront will represent the latest chapter in Goodwin's more than 100-year relationship with Boston and reaffirms our deep commitment to contributing to the growth of this world class city.”

The 100 Northern Ave. building, which will be the fourth commercial tower on Fan Pier, totals approximately 500,000 square feet of office space and more than 15,000 square feet of ground floor retail space.

Boston Mayor Walsh said at the groundbreaking, "New commercial development is driving job growth in our city—by creating jobs on the waterfront, we can help spread economic opportunity to all of Boston's neighborhoods.”

“Today's groundbreaking is another indication of the progress and momentum taking place at Fan Pier, and is a testament to the dynamic neighborhood being established on Boston's waterfront,” said Fallon Co. President and CEO Joe Fallon. “Its location, amenities and opportunities are a huge draw for some of the world's leading companies, like Goodwin Procter, which is looking to provide the best environment for its most important asset: its employees.”

With the groundbreaking for the new office building, Fan Pier, a joint venture of the Fallon Company and Mass Mutual as advised by Cornerstone Real Estate Advisers, features five high rise structures the Fallon Company has under development or completed: One Marina Park Drive, the first commercial building on the site; Fifty Northern Avenue and Eleven Fan Pier Boulevard, two towers designed for the global headquarters of Vertex Pharmaceuticals, which the Fallon Company sold to Senior Housing Properties Trust for $1.1 billion in February 2014; and Twenty Two Liberty, which broke ground in October 2013. When complete, the Fan Pier neighborhood will feature a total of eight contemporary commercial and residential luxury high-rise buildings.