The old police car they go back to get is a 1973 Ford LTD, which was the year the original The Crazies (1973) was released.
Each actor who was transformed into a "Crazy" had to sit in the make-up chair for three hours.
If you read the graffiti on the jail cell wall, one appears to say "Romero", in reference to original The Crazies (1973) director George A. Romero.
When the sheriff discovers the military plane, a satellite records his location at 40.851216 and -94.548340. These coordinates do in fact point to Iowa, but to farmland and not to the marshes as depicted. The town of Lenox, population 1401, is the closest real town to these coordinates.
Some of the filming was done in Lenox, IA. Lenox is the opposing team in the baseball scene early in the film.
Lynn Lowry: Co-star of The Crazies (1973), of which this film is a remake, is an infected local riding a bicycle through the deserted center of town.