The historic, Art Deco Pacific Telephone & Telegraph building at 140 New Montgomery is undergoing a major renovation as we speak, and they just signed their first major tenant: Yelp. As the Chron reports, the citizen-review behemoth just inked a deal for 100,000 square feet of space in the building, a third of the total available, and they plan to relocate there from their current headquarters at 650 Mission next fall.

Yelp CEO Jeremy Stoppelman says that Mayor Ed Lee's recent actions were a big encouragement in the decision to stay in the city, suspending the tax on stock options for companies going public (which Yelp recently did), and helping Yelp to get Enterprize Zone tax credits for the move.

The Chron does note that Yelp has faced some troubles during and after their IPO, including ongoing accusations of extortion by merchants who are hit up by Yelp's sales team to advertise on the site — allegedly in exchange for the removal or burial of negative reviews. Also, Yelp hasn't shown incredible profits yet, and their stock price has drifted south since their IPO in March.

In related news, Salesforce, which recently abandoned some HUGE plans to build a headquarters in Mission Bay, has inked a deal to take 80,000 square feet of office space at 600 Townsend.