MOUNT JUDEA, Ark. — Anita Hudson’s moment of realization came early this year when she saw cement trucks whizzing past her home in this blip of an Ozark town. For Sam Dye, it was when an employee at the school where he once was principal pointed out bulldozers clearing a wooded area in the distance.

For many months, Ms. Hudson and Mr. Dye had been among those who brushed off rumors that a large hog farm would be built here in the scenic watershed of the Buffalo River.

But now they were confronting reality: a farm that could house as many as 6,500 hogs was being built near them, within the pristine ecosystem of the Buffalo — designated America’s first “national river” and overseen by the National Park Service. Since then, the operation, C&H Hog Farms — which began producing piglets for the agricultural giant Cargill in the spring — has divided the community, drawn scrutiny from environmentalists, politicians, and state and federal officials, and left many wondering how one of the largest hog operations in the so-called Natural State ended up in the heart of a major tourist area.

For environmentalists, the development of the Mount Judea (pronounced Judy) hog farm provides a stark example of what they see as lax oversight of such farms by state and federal regulators. Many of them were dismayed last year, for instance, when the Environmental Protection Agency withdrew proposed regulations that would have required all concentrated animal feeding operations, or CAFOs, to submit “basic operational information” and would have increased the number of such farms that require permits.