This book is a pretty interesting read on the history and growth/expansion of in & out. https://www.amazon.com/N-Out-Burger-Behind-Counter-Fast-Food/dp/0061346721
Also, if I remember correctly he invented the drive thru as we know it today and sold the intercom patent to McDonalds I believe.
Yeah. Except they only transport their burgers (from wherever they make their burgers) as far as they can w/o having to freeze them.
I read about it in this book a few years ago. Really, really interesting.