Set to deliver in early 2015, the newest Class A office building in downtown Washington, D.C. has signed its first anchor tenant. Law firm Simpson Thacher & Bartlett agreed to occupy 40,000 square feet on the top three floors of the nine-story, 111,466-square-foot office property under construction at 900 G St. NW. The law firm committed to a 15-year lease and will relocate from its current D.C. office at 1155 F St. NW this July.