(Seattle, WA)  --  After decades of making its home in Federal Way, Weyerhaeuser [[ WARE-how-zer ]] is officially operating out of its new headquarters in Seattle.  The timber and forest products giant, founded in Longview in 1900, celebrated its grand opening yesterday at its new building in Pioneer Square.  Weyerhaeuser is touting the new headquarters as a sustainable building which incorporates a number of the company's own products.  The glass-fronted building is located on the east side of Occidental Park.