Gurnee was a town of 300 people in 1974 when village leaders were approached by developers looking to build a theme park featuring three roller coasters and a handful of other rides at the corner of Grand Avenue and Interstate 94.
The park opened two years later as Marriott's Great America, and both it and Gurnee haven't stopped growing since.
Today, the village is home to more than 31,000 residents, and the park -- sold in 1984 and renamed Six Flag's Great America -- has swelled to 100 acres filled with 14 world-class roller coasters and a 20-acre water park that have entertained 105 million customers over the years.
Former Gurnee Mayor Richard Welton said the park's arrival spurred the community's growth.
"In order to build the town into what we wanted, we needed a golden cow," Welton said Thursday during a special ceremony at Great America. "You are looking at that golden cow."
Welton was one of about 100 Gurnee residents in attendance when Great America officials announced they would turn back the clock next year to celebrate the theme park's 40th anniversary.
The "40 Seasons of Thrills" will include returning the Carousel Plaza and Hometown Square areas of the park to its classic feel and reintroducing the Tots Livery Surrey Carriages, the Red Baron Airplanes and the Lady Bugs, three classic children's rides that were part of the park's original lineup.
Officials also said they will also host special events at each roller coaster throughout the 2015 season.
"It's amazing when you think back on it," said warehouse supervisor Rich Neal, who has worked at the theme park since it first opened May 29, 1976. "It's like watching your kids grow up. When you see it a little at a time, you don't notice. But the contrast from then until now is amazing."
Park President Hank Salemi and Gurnee Mayor Kristine Kovarik joined Welton during the ceremony announcing the 40th anniversary celebration, which will include a special party May 29.
Welton said that when Marriott Corporation came to the village to talk about Great America, he followed one simple rule.
"We're not against development as long as it pays for itself." he said.
By collecting a small amount of amusement tax from the 105 million people that have walked through the park's front gates over 40 years, he said, the village has easily followed that rule.
"We are so lucky to be in the community we are in," Welton said.