Archibold Cox was named as Solicitor General by JFK.
JFK had first come into contact with Cox in 1953 when he was looking to develop an expertise in labor law. Kennedy contacted Cox, who was a professor on the Harvard Law School faculty and invited him to appear before a House committee to testify.
Prior to his appointment as Solicitor General, Cox had worked in the department as an associate solicitor.
[152, p. 47]
[wikipedia entry, Archibald Cox]