1201 Third Avenue is a 235.31-meter, 55-story skyscraper in Downtown Seattle, in the U.S. state of Washington. It is the third-tallest building in the city, the eighth-tallest on the West Coast of the United States, and the 97th-tallest in the United States. Developed by Wright Runstad & Company, construction began in 1986 and finished in 1988. 1201 Thiā¦1201 Third Avenue is a 235.31-meter, 55-story skyscraper in Downtown Seattle, in the U.S. state of Washington. It is the third-tallest building in the city, the eighth-tallest on the West Coast of the United States, and the 97th-tallest in the United States. Developed by Wright Runstad & Company, construction began in 1986 and finished in 1988. 1201 Third Avenue was designed by Kohn Pedersen Fox Associates and The McKinley Architects. The building was the world headquarters of the financial company Washington Mutual from the building's opening until 2006, when the company moved across the street to the WaMu Center.