filming location

I'll try to look closely at the closing credits to see if it thanks anybody. I'd imagine most of this was filmed on public grounds like a state or county park. I'm also not hearing any southern drawl or accents in the cast, and the dreary locations remind me a lot of what I know of Pennsylvania. The presence of George A. Romero actor John Amplas also suggests a PA setting.

According to various horror film review guides this film was shot in Pennsylvania.

I'm a totally bitchin' bio writer from Mars!

Just to muddy the waters further...

(and, by the way, should all of those characters really be drinking creek water so casually? Don't they risk catching listeria or something?)

...the license plate on the Peugeot station wagon has black numbers on an off-white background. That was not the color scheme for plates in PA, but it was the color scheme in TN... until 1977. How many years did CM take to make this movie?

On the other hand, when the car pulls up to the gas station at the end, it has big patches of body rust, which might suggest a more Northern locale (road salt and all)-- except the car is a Chevy Vega, so all bets are off!