In this letter, the Postmaster General Amos Kendall responds to S.W. Benedict of New York City explaining that Benedict’s mail was returned because it contained abolitionist sentiment. Even though the surveillance and return of properly mailed materials went against federal law, many Southern post offices followed state laws which prohibited the delivery of abolitionist literature.
“An Abolition Paper of the Deepest Dye” 1835
National Archives, Records of the Post Office Department