The Minnesota Department of Natural Resources on Monday denied a rare request from the city of St. Francis to loosen the rules for development along the Rum River, one of six rivers protected by the state’s Wild and Scenic Rivers Program.

City officials had petitioned the state to allow denser development options on smaller lots near the river, similar to what’s already permitted in more built-out areas along the Rum. Officials say that the nearly 500 acres included in the petition, much of it farmland, is key for future growth in the northern Anoka County community of 7,500.

But in its decision Monday, the DNR said the city’s request runs contrary to the Rum’s scenic designation, which aims to protect the river’s natural character from development pressure.

“We are still happy to work with the city to try to find some way for them to develop within the realm of the rules,” said Dan Petrik, who manages Minnesota’s program. “We don’t know what path that might take yet.”

Petrik said the city can appeal the DNR’s decision. Mayor Steve Feldman declined to comment Monday.

St. Francis’ petition is believed to be the first of its kind for the state’s Wild and Scenic Rivers Program. The Rum was added to the program in 1978.

In planning for growth, St. Francis wanted to cut the minimum lot size requirements on land next to the river from 4 acres (about 174,000 square feet) to 20,000 square feet. The petition also asked the state to consider reducing lot width minimums and river setbacks, among other changes.

City officials say that St. Francis’ wetlands limit options for building in other parts of the community, and that much has changed in the 40 years since the state rules were put in place.

The DNR describes the city’s requests in Monday’s 35-page decision as “significant deviations from the rules” and notes that “any public interest in high-density development does not outweigh the state’s express and paramount interest in protecting Minnesota’s wild, scenic and recreational rivers.”

City officials have said they are not pushing for development so much as seeking flexibility for growth should landowners decide to sell their open acreage.

The topic has stoked fierce debate in northern Anoka County and beyond, with the DNR fielding more than 200 public comments ahead of Monday’s decision.

Those supporting the city’s request have noted that denser development could help the area draw more jobs and businesses and unlock a bigger tax base.

Critics of the petition worry it undermines the purpose of the Wild and Scenic Rivers Program and could set a troubling precedent.

Homeowners near the Rum say they were drawn to the area for the quiet woods and wildlife next to the narrow river that meanders south about 150 miles from Lake Mille Lacs to the Mississippi River.

“This is a treasure,” said St. Francis resident Michael Minkler, who has lived on the Rum for more than 20 years. “I want to pass it on someday.”