- Manuscript draft of a twelve-page letter from Lysander Spooner in Worcester [Massachusetts] to Gerrit Smith, dated April 23, 1850, in which Spooner discusses specific instances of copyright infringement committed by Smith in the publication of "Gerrit Smith's Constitutional Argument.", New-York Historical Society
- Three-page letter dated April 15, 1853, from L. [Lysander] Spooner in Boston [Massachusetts] to [George] Bradburn, notifying him of the death of Ernest Hidlreth, the youngest child of Richard and Caroline Hildreth, as well as discussing Spooner's newest work on the "Law of Intellectual Property" and a controversy between Horace Mann and Wendell Phillips., New-York Historical Society