By the time Ike appointed him, he was long past the practice of law, having been a politician for many years.
However, he got his start in politics as District Attorney of Alameda County. He served three four-year terms, starting in 1925, after which he graduated to California Attorney General in 1938, followed by Governor for three terms. He lost out as Dewey's VP in 1948 (they were ahead in the polls).
In 1953, Eisenhower appointed him Chief Justice.
Yet I clearly remember the knock on him at the time was that he wasn't qualified because he had no training or experience with the law.
Whoever was making that claim was clearly wrong.
And, to my chagrin, I've been repeating it for the past fifty years...