Headquartered in San Francisco, California, the United States Court of Appeals for the Ninth Circuit is the nation's busiest federal appellate court. Judicial districts within the Ninth Circuit include the districts of Alaska, Arizona, Central California, Eastern California, Northern California, Southern California, Hawaii, Idaho, Montana, Nevada, Oregon, Eastern Washington, Western Washington, the U.S. Territory of Guam and the Commonwealth of the Northern Mariana Islands. The establishment of the Ninth Circuit in 1866 began the development of the federal judicial system for the western United States. The court's regular meeting places are Seattle at the William Kenzo Nakamura United States Courthouse, Portland at the Pioneer Courthouse, San Francisco at the James R. Browning U.S. Court of Appeals Building, and Pasadena at the Richard H. Chambers U.S. Court of Appeals.