The federal crime of mail fraud is generally viewed as the original federal auxiliary jurisdiction crime, that is, a crime that does not protect direct federal interests against harm. Rather, it functions as an auxiliary to state crime enforcement. In the almost 150 years since Congress enacted the mail fraud statute, federal auxiliary crimes have proliferated and have become the most important part of federal criminal jurisdiction—so that, today, they largely duplicate state crimes. It is important to know how this form of federal criminal jurisdiction originated.

Mail fraud is a crime that scholars, judges, and lawyers have viewed as having almost no legislative histories linked to its original enactment in 1872 and its two revisions in 1889 and 1909. The details of its origins have remained generally unknown.

This paper breaks new ground by uncovering a rich set of legislative history details related to each of those three early statutes. Inter alia, these legislative history materials reveal that the original mail fraud provision might not have been drafted and enacted except for the fortuitous timing of the addition of a criminal penalty to a closely related statute. It also explains how mail fraud came to be the original federal auxiliary jurisdiction crime; that was not the original intention.