There are 13 judicial circuits, each with a court of appeals. The smallest court is the First Circuit with six judgeships, and the largest court is the Ninth Circuit, with 29 judgeships. A list of the states that compose each circuit is set forth in Title 28 of the U.S. Code, Section 41. The number of judgeships in each circuit is set forth in Title 28 of the U.S. Code, Section 44.
There are 89 districts in the 50 states, which are listed with their divisions in Title 28 of the U.S. Code, Sections 81-144. District courts also exist in Puerto Rico, the Virgin Islands, the District of Columbia, Guam, and the Northern Mariana Islands. In total there are 94 U.S. district courts. Some states, such as Alaska, are composed of a single judicial district. Others, such as California, are composed of multiple judicial districts. The number of judgeships allotted to each district is set forth in Title 28 of the U.S. Code, Section 133.