Hmmm. I thought the last functioning drive-in theatre closed about a decade ago. IIRC, it was in Califonia.
There were two in the SF Bay Area I remember: the Island Auto Movie in Alameda (closed after a storm in 1991, demolished 1997), and the Union City Drive In (closed March 31, 1998).
There is one at Springdale and Marshall Arkansas.
I have 3 of them near my house.