The United States Court of Appeals for the Tenth Circuit hears appeals from the district courts of the states of Colorado, Kansas, New Mexico, Oklahoma, Utah, and Wyoming. With one exception, each state is a single federal district, for example the District of Colorado.
Oklahoma, however, is divided into an Eastern, a Northern, and a Western district.
Why? Are the federal courts of Oklahoma busier than those of the other states? The obvious answer is population, but Colorado is substantially more populous than Oklahoma. Nor is the population of Oklahoma more dispersed than, say, that of Kansas.
How did this happen? Is there a reason for it?