Erle Stanley Gardner

The creator of Perry Mason, arguably the most famous fictional lawyer in history, was himself a practicing attorney for over 20 years.
He passed the bar exam at the age of 21.
His Perry Mason stories were so popular that he wrote six novels a year plus short stories for magazine publication.
Used pseudonyms for some of his works, including Carleton Kendrake and Charles J. Kenny. However, A.A. Fair was the most popular of his pen names. Since Gardner was such a prolific writer, the pseudonyms were necessary to sell other works, lest the market be flooded.
Wrote for the popular pulp detective magazine "Black Mask" on a sporadic basis in the early 1920s (creating wildly popular "Ed Jenkins, Phantom Crook" stories in 1925). He continued to write pulp stories for the magazine into the 1940s.

[on Perry Mason, as explained to his publisher] The character I am trying to create for him is that of a fighter who is possessed of infinite patience.
If you started to write, you did it because you had an urge to express yourself. That urge is a part of you. It's still there....
I still have vivid recollections of putting in day after day of trying a case in front of a jury, which is one of the most exhausting activities I know about, dashing up to the law library after court had adjourned to spend three or four hours looking up law points with which I could trap my adversary the next day, then going home, grabbing a glass of milk with an egg in it, dashing upstairs to my study, ripping the cover off my typewriter, noticing it was 11:30 p.m. and settling down with grim determination to get a plot for a story. Along about 3 in the morning I would have completed my daily stint of a 4,000-word minimum and would crawl into bed.