This movie is one of several fictional adaptations of a true, famous legal case of imposture from sixteenth century France. The case involved a man named Martin Guerre who, having disappeared from his Basque village in 1548, suddenly reappeared eight years later. Despite his slightly changed appearance, he convinced his family, wife, and fellow villagers that he was indeed Martin Guerre; he and his wife had two more children and he sued a paternal uncle for the claim to his father's estate. That uncle became suspicious that this returned Martin Guerre was actually an impostor named Arnaud du Tilh, and he contrived a way to have him tried for imposture. This suspicion was ultimately confirmed when the actual Martin Guerre arrived in court during du Tilh's trial. Arnaud du Tilh was convicted and hanged in September 1560.
The film unit also had to deal with torrential rain and flash floods, in which Gere became a hero, personally rescuing horses and livestock from probable drowning. Film extra Billy Russell recalls, "They were filming a scene when the heavens opened. The river which had been swelling after heavy rains all month, burst its banks and all hell broke loose. The cast and crew fled indoors to wait until it had passed, when Gere remembered the horses tied up in a nearby stable. Still wearing his Civil War costume, he waded through the water and by the same time we reached the stables, the water was quite high, really dangerous. He untied his own horse and then supervised the removal of all the livestock to a safer area."
Original writer Nicholas Meyer walked off the production when Warner Brothers wouldn't let him direct his screenplay. Sarah Kernochan was drafted in to rewrite the script and was somewhat bemused to see that it was an Americanized version of The Return of Martin Guerre (1982). Warners denied this in a rather obvious attempt not to have to buy the remake rights, but Kernochan insisted that they do before continuing as they weren't fooling anyone. Warners eventually relented, and also gave Meyer story credit.
Sommersby is the first motion picture allowed to shoot in the George Washington National Forest. Not one hole could be dug by the construction crew without an accredited archaeologist being present to look for remains of habitation that might date back over 9,000 years.
It was on the set of this movie that star Jodie Foster met her longtime romantic partner Cydney Bernard, who was working as a production coordinator. They had two children together and remained a couple until their 2008 break-up.
Steven Reuther, one of the producers behind the project commented about the casting of Gere and Foster: "A lot of people questioned us about this coupling. And it was a gamble, because there are the obvious romantic leading females, and Jodie really is not one of them. Also, I don't think anyone had ever seen Jodie in a period costume. But once we got her in the period clothes and the hair, it was like, 'How could there have been a question?' I think that part of why she was attracted to the character was because it was something she had never done before."
The origins of Sommersby began when, Richard Gere and his production company partner Maggie Wilde, began searching for projects which he could be involved in from the beginning and retain some control over. One of the scripts he found was Nicholas Meyer's Sommersby which had recast the sixteenth-century French legend into the era of the American Civil War. Gere discovered that the script was controlled by the co-producers of Pretty Woman, Arnon Milchan and Steven Reuther. He contacted them and it was not long before the production was underway. Gere was to star in the film himself and they chose Jodie Foster as the leading lady. Foster had recently won an Oscar for her role in The Silence Of The Lambs. Bill Pullman and James Earl Jones were also cast as the love interest and courtroom judge respectively.
Warner Brothers were behind the project and, as this was to be an expensive film with period costumes, sets and animals, a budget of $20 million was put in place. British director Jon Amiel was called in to direct and Gere brought in an additional, uncredited writer, Charlie Mitchell, to rework some of the scenes and provide accuracy in regional dialogue.