With speculation of Kamala Harris getting pushed into the Supreme Court, I'm wondering when if ever something like this has happened before. Has anyone ever been appointed to the Supreme Court without prior experience as a judge? And if so, when was the last time this has happened?
Quite a lot of them have been, in fact. There have been 115 Justices in the court's entire history, and the linked page indicates that 41 of them, more than a third of all Justices in the court's history, had no prior judicial experience before their appointment. The most recent, as indicated in another answer, was Elena Kagan in 2010. We even have a Q&A about her confirmation sans judicial experience.
Indeed, of the 17 different Chief Justices, nine of them, more than half, had no prior judicial experience before appointment to the court! Three of those were already an Associate Justice when they were nominated to be Chief Justice, at least. See the link for full details, but here's a few of the more notable Chief Justices that had no prior experience.
- John Marshall (1801-1835, the longest serving Chief Justice ever, and thought to be one of the most influential Justices ever; decided the case Marbury vs. Madison, which entrenched judicial review and let courts decide constitutionality of laws)
- Salmon Chase (1864-1873; was the Chief Justice presiding over the first Presidential Impeachment trial)
- Earl Warren (1953-1969; his court and the subsequent Burger court are considered some of the most liberal in history; also the last such ones)
- William Rehnquist (1986-2005; the Chief Justice immediately preceding the current Chief Justice Roberts)
Elena Kagan in 2010.
After graduating from Princeton University, the University of Oxford, and Harvard Law School, she clerked for a federal Court of Appeals judge and for Supreme Court Justice Thurgood Marshall. She began her career as a professor at the University of Chicago Law School, leaving to serve as Associate White House Counsel, and later as a policy adviser under President Bill Clinton. After a nomination to the United States Court of Appeals for the D.C. Circuit, which expired without action, she became a professor at Harvard Law School and was later named its first female dean.
In 2009, Kagan became the first female solicitor general of the United States. President Obama nominated her to the Supreme Court to fill the vacancy arising from the impending retirement of Justice John Paul Stevens. The United States Senate confirmed her nomination by a vote of 63–37.
Prior to Kagan, was William Rehnquist in 1972.
Before Rehnquist, was Lewis F. Powell Jr. on the same day as Rehnquist. While Powell was also without prior judicial experience, Powell was given seniority on the Court by a few minutes.
On the rare occurrence that two Justices join the Court on the same day, seniority is determined by age. This occurred on January 7, 1972, when Lewis F. Powell, Jr., and William H. Rehnquist were sworn-in during a special sitting of the Court. Although Rehnquist had taken his Constitutional Oath prior to Powell, Chief Justice Burger administered the Judicial Oath to Powell (age 64) before Rehnquist (age 47).