Parts of a remote central Utah canyon decorated with ancient Indian art are being nominated for the National Register of Historic Places.

The Bureau of Land Management last week nominated 63 sites along Nine Mile Canyon, which some call the world's longest art gallery. It contains more than 10,000 prehistoric rock carvings and paintings of bighorn sheep, owls, a two-headed snake, spear-wielding hunters and warriors engaged in hand-to-hand combat.

In the coming years, the BLM in Utah plans to nominate more than 800 sites in the canyon for the national register, according to Megan Crandall, an agency spokeswoman in Salt Lake City. She said it's the largest such attempt for archaeological sites in Utah.

The canyon is a prized destination for rock art enthusiasts. It's also been a place of controversy because of plans for nearby mineral development.

The BLM is about to launch another in-depth study on the nearby West Tavaputs Plateau. The agency has been considering a proposal that would allow about 800 more natural gas wells in the area and increase truck traffic on the narrow, 78-mile road that snakes through the sandstone and shale canyon.

Conservationists worry the extra truck traffic would kick up dust in the canyon and jeopardize the irreplaceable rock art.

Listing on the National Register is an honorific designation and wouldn't provide additional protections for the canyon's petroglyphs and pictographs. It may, though, prompt decision-makers to be more thoughtful about development in the area, said Wilson Martin, Utah's state historical preservation officer.

"People come from all over the world to see this level of concentration," Martin said.

Pam Miller, chairwoman of the Nine Mile Canyon Coalition, which advocates for the canyon's protection, said her group is thrilled by the nominations — first sought more than 30 years ago — even though they would have preferred creation of a historical district rather than nominations for individual properties.

"What this listing will say is this is a place that's valued in this country," Miller said. "It doesn't stop anything but it's another way to get it on the table for discussion."

The canyon's drawings and carvings, easily spotted today from the unpaved road, have been a source of fascination and speculation since their discovery in the late 1800s. Some of the art is believed to be the work of the mysterious Fremont people, who lived in present-day Utah, Idaho, Colorado and Nevada from A.D. 700 to 1300.

Other inscriptions in the canyon's walls are from the Ute Indians, early explorers and members of the U.S. 9th Cavalry.

The first batch nominated for the National Register includes 19 rock art sites, 40 that include evidence of people living and working during the Fremont period and four sites with homesteads and cabins from the late 1800s and early 1900s. All the proposed properties are on BLM land.

The public has until Nov. 25 to comment on the nominations.

The next round of nominations likely won't be finished until next year.

Crandall said the designation for portions of Nine Mile Canyon, which is a mix of public and private property, is a clear statement of the area's cultural importance.

The National Register is administered by the National Park Service. The BLM says about 30,000 properties are added to the list each year, often for historical buildings or districts.