Okay, after having done a little bit of googling, I found that Rothbard himself wrote about it in For a New Liberty. I had only previously heard him mention it in the end of his lecture on the legacy of the Civil War but he addresses it here, starting on page 256. Following his footnotes leads to E. Louise Peffer’s The Closing of the Public Domain.
Pages 22-31 are directly relevant and available to read in the preview.
*Edited the link.
