Georgia-based Wells REIT II has acquired IBM’s regional headquarters complex in Littleton, the state’s largest software campus.

The IBM Littleton campus at 550 King St. was built for Digital Equipment Corp. in 1984. The property was vacated prior to acquisition by Angelo Gordon and National Development in 2006, and then underwent a major renovation in 2008. IBM has consolidated roughly half of its 5,000 regional employees to the site.

The 490,000-square-foot Class A office complex is leased to IBM until 2020, according to a statement.

"This is a great acquisition for our portfolio, and we are thrilled to add IBM Littleton to the Wells family of tenants," said Don Henry, chief real estate officer. "IBM is one of the strongest names in international business, and we look forward to serving their real estate needs in Massachusetts for many years to come."

Wells REIT II acquired the property from a joint venture of Angelo Gordon and National Development, who bought the building in 2006 for $25 million. It was assessed for $30 million in 2009, according to data from The Warren Group, publisher of Banker & Tradesman.

Wells was represented internally by Heather Griner, senior vice president, Capital Markets. Wells negotiated the transaction off-market with the sellers.

"We like the property, and we felt it was an especially good opportunity in the current real estate environment," Henry said.