Luv In-And-Out. Still family owned, no franchises, so that's why the expansion has been limited. The "first drive through" got me looking around. In-and-Out's web site only claims to be the first in California (1948), while Wikipedia, that always-reliable source (?), says it was invented at Red's Giant Hamburgs on Route 66 in Springfield, MO. Our (San Diego) own local chain that grew into a monster, Jack-In-The-Box, started with drive throughs in '51.
Always curious about the drive throughs.