In the study of criminal law, why is it essential to understand the significance of the common law of the United States?

The common law was the backbone of the United States, but today the states have codified most of their criminal law into legal codes. Today's codes or statutes are the source of criminal law and have replaced the common law. The common law is used more as reference for definitional purposes. Some states use the common law to govern, Perfect example would be Pennsylvania which had no statue on "harassing phone calls" and suggesting "obscene sex acts". The state looked into the common law and found a misdemeanor and was able to charge the perpetrator. This conviction would have not been possible in a jurisdiction that had abolished the common law offenses, if there were no statute. It is significant to understand common law because state and federal judiciary frequently reference common law to interpret offenses.

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