When Supreme Court Justice Tom Clark resigned his seat on the bench at the youthful age of 67 after 18 years, his decision was unique in the annals of Court history: he was leaving so that his son Ramsey, just nominated as Attorney General, could assume the job Clark himself had once held without conflict of interest.

As Alexander Wohl shows, Tom and Ramsey Clark had a profound impact on American law and society. For nearly three quarters of a century, they influenced presidents, policies, and legal rulings, during careers that tracked closely with some of the most significant and...