The 4-H Horse'n Around Club drill at the Montgomery County Fair in Gaithersburg, MD on August 10, 2012. (Linda Davidson/THE WASHINGTON POST)

Like clockwork, the chickens, the sheep, the tractors and the Ferris wheel are driven onto a 63-acre plain in the heart of Gaithersburg. It’s done every year around this time as part of a major annual event in the region: the Montgomery County Agricultural Fair.

But the six-decade institution, which kicked off Friday, is on the brink of change. Sometime soon, the animals, the carnival rides and even the fair itself could leave the Gaithersburg Fairgrounds for good.

The Gaithersburg City Council rezoned the fairgrounds in June, allowing large redevelopment for the first time. The Montgomery County Agricultural Center organizes the fair and owns the land and said it has no plans to sell the land or move the fair. But its efforts to support the rezoning have led some to fear that the fair could leave.

“That land will probably be prized land for commercial [entities],” said B. Marie Green, county supervisor for the state’s Department of Assessments and Taxation. “I can see in 10 years, they’ll do something with it.”

Martin E. Svrcek, the center’s executive director, said that moving to a new location would be difficult and that the organization likes being in Gaithersburg. But the center’s board of directors wanted “to prepare for the future,” he said, and has identified another possible location for the fair — an 84-acre farm in Boyds.

Gaithersburg Mayor Sidney A. Katz said there are rumors that the center might sell the fair because of the rezoning, but he added that the designation could lead to higher property values for the fair and the opportunity to secure loans to renovate the property.

“If [a move] were to happen, it wouldn’t happen for a long time,” Katz said.

On Friday, many at the fair said they had heard the rumors, too, but hoped they were not true.

“I guess I’m a traditionalist,” said Oriole Saah, 45, as she held her 4-year-old son next to the 4-H equestrian show. “The county fair represents the history of the county . . . and I’d hate to lose this.”

Boy Scouts from Rockville guided cars into parking spots, and farmers were getting their animals ready for competition. Using shears and clippers, 37-year-old Bruce Snyder shaved the wool off a sheep but left a layer around its feet. His Kutztown, Pa.-based Snyder Farms has been competing at the fair for at least 25 years, and he hopes to win — and to keep coming back.

“I’ve heard rumors for the last 10 years at least,” said Forrest Snyder, Bruce’s father. “I understand this to be a landmark in Montgomery County. . . . I’d like to see it stay.”

For decades, no one thought the fair would move. Organizers purchased the land in 1949, and every year dozens of volunteers helped set up the lights and prepare the animals. Dozens of volunteers became hundreds, and the fair evolved into a city tradition. “There have been families [volunteering] for several generations,” Katz said.

In 2003, city planners recommended that the land largely be open space. Three years later, the center’s board crafted a strategic plan that included rezoning. The organization hired a Columbia-based planning firm to sketch mixed-used plans for the property, and it applied for the rezoning in October 2010.

City officials held meetings over 16 months and unanimously approved the land-use change June 18. Now, if the center allows it or decides to sell the land, developers can construct buildings up to 15 stories tall.

Once the fastest-developing area in the county, the city is reaching its build-out limits and city planners have recently identified properties that are good spots for mixed-use development. Meanwhile, the city in 2010 approved its first property tax rate increase in 45 years and slashed spending by 8 percent to balance its budget.

The fair has gone through changes over the years. Katz said that when he was in high school, fellow students from nearby farms would come to the fair to show off their cattle. “Now, people bring their children to the fair to show what cattle looks like,” he said. “This was a really agricultural area 30 years or 40 years ago. Today we’re not nearly as agricultural.”

The value of the land has fluctuated in recent years. Adjusted to today’s dollars, the property was worth $17 million in 2006 and $19 million in 2009. Now, as property values have plummeted nationwide, it’s worth $14 million. But Green said the value of the property will probably increase because of the rezoning. The fairgrounds are surrounded by Interstate 270 and routes 117 and 355 — major county thoroughfares — and are a few blocks from the city’s MARC station.

“With the size of that property, it’s going to be a lot of money, a lot of money,” Green said. “Let’s just say a lot of people will want it.”

Svrcek said the center has fielded calls occasionally from people interested in purchasing the property. So far, he said, the answer has been the same: The fair is staying.