How many appellate districts or judicial circuits are there?

In the United States, there are 13 appellate courts, known as U.S. Courts of Appeals, which are divided into 12 regional circuits and one Federal Circuit. Each circuit hears appeals from federal district courts located within its jurisdiction. Additionally, many states have their own appellate districts or circuits, which vary by state. For example, California has six appellate districts, while Illinois has five judicial circuits.