The US federal legal system is divided into Circuits and then Districts that can be further subdivided into Divisions in large states. Thus there are 94 Federal Districts for 677 authorised (as of spring 2022) District Judges, with at least one per state, plus the District of Columbia, Puerto Rico, the Virgin Islands, Guam, and the Northern Mariana Islands. Some states have multiple judicial districts, sometimes for historical reasons, sometimes for modern geographical reasons – so that North Carolina has 3 judicial districts with 12 divisions, while California, a much larger state in population and geography has 4 districts with 15 divisions, while a few states, Delaware, Rhode Island and New Hampshire have just one district and one division. Fifty five Federal Districts are divided into multiple divisions – so that Texas has 4 districts (Eastern, Western, Southern, Northern) divided into 29 divisions. Each division usually has a single courthouse. Some divisions are single judge units and there is controversy that this allows forum shopping to extend to judge (or Division) shopping.
Above the federal district court level, the courts of appeals are divided into 13 circuits, 12 numbered plus the Federal Circuit which hears appeal of appeals of patent cases, appeals of USPTO decisions, and appeals from the United States Court of Claims.