Harvard completed a $168.5 million sale of Watertown’s Arsenal on the Charles to electronic health records company athenahealth, Inc., according to a Monday announcement by real estate firm Avison Young.

The sale, which was announced in December, includes the entire 11-building office park that sits on the Charles River less than 10 miles outside of Boston.

The 29-acre site was originally an armory for American troops in the Civil War and first and second World Wars and includes buildings that are around 200 years old. As an office park, the Arsenal on the Charles has served as athenahealth’s headquarters since 2005, and the company already takes up a large portion of the property’s 760,000 square feet.

A Harvard spokesperson said in December that Harvard has been reviewing its off-campus properties to see if they fit with the University’s mission of education and research—a process that led administrators to sell the property.

In the press release, athenahealth CEO Jonathan S. Bush said that the property’s location made it particularly attractive for the company’s expansion.

“We are excited to deepen our roots in Massachusetts; Watertown is our home,” Bush said. “The Arsenal on the Charles offers athenahealth everything we could ask for in a headquarters; its open and expansive architecture, outdoor campus feel, strong community, and proximity to Boston fit with our culture, strengthen our standing as a top employer, and provide an inspirational backdrop as we work to be medical caregivers’ most trusted service.”

—Staff writer Samuel Y. Weinstock can be reached at sweinstock@college.harvard.edu. Follow him on Twitter @syweinstock.