In a recent social media discussion someone raised the issue of Murray Rothbard's relationship with Milton Friedman. I reported that Rothbard had a good relationship with Friedman and other academic libertarians in the 1950s and early 1960s, with Friedman even recommending Rothbard for a post at Chicago. Thanks to the Mises Insittute's archivist Barbara Pickard I have the details handy. In early 1956 Friedman discussed with Richard Cornuelle, then running the Volker Fund, the possibility of getting Rothbard to Chicago for a postdoctoral fellowship. Friedman wrote that he and his colleagues "would be delighted to have Rothbard apply for one of these" and that "I am sure he will be considered very favorably" though he could not guarantee acceptance. Ultimately, Rothbard decided not to apply, presumably because of his strong preference to remain in New York. It's interesting to wonder how the academic libertarian movement might have developed if Rothbard had gone to Chicago.
More generally, Rothbard and Friedman reportedly had a cordial relationship until the early 1960s. According to Rothbard: "There was another group coming up in the sixties, students of Robert LeFevre’s Freedom School and later Rampart College. At one meeting, Friedman and Tullock were brought in for a week. I had planned to have them lecture on occupational licensing and on ocean privatization, respectively. Unfortunately, they spoke on these subjects for thirty minutes and then rode their hobby horses, monetary theory and public choice, the rest of the time. Friedman immediately clashed with the Rothbardians. He had read my America’s Great Depression and was furious that he was suddenly meeting all these Rothbardians. He didn’t know such things existed."
By 1971 Rothbard's view of Friedman became highly critical, as described in his essay "Milton Friedman Unraveled," in which he described Friedman as "the Establishment's Court Libertarian."