"Most of them are just delighted to reflect and remember," said Wendy Nagle, president and CEO of the bureau.
The tour's main attraction is the 82-acre Strasburg-area farm where Philadelphia cop John Book (Harrison Ford) and Amish widow Rachel Lapp (Kelly McGillis) fall in love and struggle to understand one another's worlds.
The bus first takes tourgoers to downtown Lancaster's Cultural History Museum to see its Witness to "Witness" exhibit. The museum's first two floors highlight Amish life and "Witness" memorabilia, while the top level is dedicated to the movie's famous barn-raising scene.
The exhibit points out discrepencies even the most devoted fans may not have known about the film. Rachel Lapp, as a widow, should have worn black for at least a year, yet the movie shows her dressed in an array of colors and patterns, some of which do not follow Amish tradition. Hollywood isn't always reality, said 25-year tour-guide veteran John Graham.
"My guess is she was too pretty of a girl to be wearing black the whole movie," Graham said.
The tour has failed to attract a significant local following, said Peter S. Seibert, president of the Heritage Foundation of Lancaster.
"I hope people in Lancaster take the tour because it's not going to be here forever," said Seibert, who also serves as director of the Cultural History Museum. "The farm may not be accessible after the tour concludes."
"Witness" fans still remember Sam Cooke's hit "Wonderful World" playing on a car radio as John Book and Rachel Lapp came together for a forbidden dance in the barn's shadows.
"That's her favorite scene," said Lew Williams, pointing to his wife, Trish.
The Williamses live in Camp Hill but are both from Illinois, where a large sect of Amish lives today. The Plain folk of Illinois are just not the same, Williams said."Maybe it's the rolling hills, but there's a quaintness (in Lancaster)," he said. "It isn't nearly the same kind of appeal (in Illinois) you have here."
The couple agrees "Witness" made Lancaster an appealing place to visit.
The film has always carried a strong cult following, Seibert said.
"There are people that are really fanatical about the movie, and they'll be like, 'Where was this scene shot?' and so on and so forth," he said.
Nagle didn't anticipate such a devoted "Witness" fanbase.
"We found out that visitors are very curious about tidbits about the movie," she said. "They all of a sudden had to become trivia buffs."
Martha Beiler stood on her home's front porch, where Ford and McGillis once stood themselves. Here she greets the many visitors that come and go from her farm, purchased with her husband, Ivan, in 2001.
A woman leaned down and looked into the round eyes of Beiler's daughter. Unfrightened, the child stared back, her face framed by the layers of a navy scraf.
"Can you wave 'bye?" the woman asked the toddler.
The Amish girl did not respond.
"She probably doesn't understand what I'm saying," the woman said.
Twenty years later, the movie may still define the area, but it will never define the Amish.
"For many people, I'm sure, everything they learned about the Amish they learned from Witness," Graham said.
The three-hour tours leave the Visitors Bureau at 9:30 a.m. and 1:30 p.m. on Monday, Friday, and Saturday through Nov. 21. Cost is $29.95 for adults and $12.95 for children ages 12 and under. Tickets can be purchased by calling 1-800-PA-DUTCH.