Factual error: Not only is the tractor the wrong vintage, it is pulling a round baler that wasn't invented until the 1970's.
Continuity mistake: Driving to the bridge the landscape (a farm with a red and a yellow house) in the background (behind Meryl Streep) is seen twice. And many of the houses seen through Meryl's truck window are modern, not old farm houses. (00:21:35 - 00:22:45)
Factual error: In one scene they are playing "Almost Like Song." Although it had someone singing it to give it an old timey sound, the song wasn't released until 1977, 12 years after this is set.
Factual error: The red truck is shown to have 1991 license plates, although the film is set in the 1960's. Also near the end, when Meryl Streep is riding in her husband's truck through town, many modern cars are seen in the background through the truck window.