As Facebook plans to expand its presence in Kendall Square next year, the company's big return to Cambridge could be seen as a feather in the cap of House Speaker Robert DeLeo, who for years has been pushing the social media giant to come back to where it was invented.

DeLeo isn't on Facebook himself, but in 2012 he wrote an open letter to founder Mark Zuckerberg to convince him to move the company back to Massachusetts, where Zuckerberg first created the site from his Harvard dorm room. Facebook's headquarters isn't moving out of Silicon Valley, but DeLeo is pleased with the Kendall Square expansion.

"I'm really excited. They're going to be ... one of our larger employers in Cambridge," DeLeo told WGBH News.

Facebook plans to more than triple its workforce in Massachusetts, from 150 employees to 650.

"When you're talking about 500 people, to me, that sends me a signal that 'yeah, I am thinking about -- we're looking at Massachusetts a lot more seriously," DeLeo said.

DeLeo credits the state's emphasis on economic development and innovation, as well as the education system and political climate, for drawing in large tech companies.