Mr. West published thousands of cases in his National Reporter System so cases from all jurisdictions were available for the first time. With all the cases out there he had to develop a method to find cases on a specific topic.
In 1848 West developed a classification system called the West Digest System to assist researchers in finding case law. The West Digest System is composed of topics and Key Numbers. It is now called the West Key Number System and is available on Westlaw.
He decided that all legal issues fall into one of 414 broad topics. Each topic is divided into numerous subtopics, each of which is assignment a Key Number. There are over 90,000 Key Numbers.
When you are reading a useful case, locate any useful Key Numbers and click on them to find cases on the same topic.