A new exhibit of Native American petroglyphs opened quietly this spring in the Columbia River Gorge, which marks the border between the U.S. states of Oregon and Washington. The region once held one of the richest deposits of tribal rock imagery in the world. But hundreds of the petroglyphs were submerged under water in the 1950s, when the federal government dammed the river. Some of the petroglyphs were rescued before the flooding, and now federal officials are trying to make amends.

Five years ago, U.S. Forest Service archeologist Jim Keyser stood at the base of the gargantuan slab of concrete known as the Dalles Dam. Lining the parking lot were 43 chunks of rock, covered with Native American figures chiseled in the former cliff face hundreds if not thousands of years ago. They were also coated with more modern bird droppings.

"See, there's an example, you can't even tell what that was is because it's covered with so many bird droppings, right? That's like having the Mona Lisa just sitting under a dam just open to the air. It's fantastic imagery," he said.

Even more significant than famous artwork, each rock image holds spiritual significance to northwest tribes. There are stick figures of deer and elk, swirling lizards, and haunting owls.

Today those 43 boulders are no longer in the shadow of the Dalles Dam. After years of negotiations and effort, they've been moved and delicately cleaned and restored.

At her office in Portland, Gail Lovell shuffles through drawings of the new petroglyph display she helped organize. She works for the U.S. Army Corps of Engineers, the same federal agency that submerged most of the tribal petroglyphs in the gorge in the 1950s.

"I'm a new generation," said Gail Lovell. "And over the years we've developed a relationship of bringing back some trust."

Last fall, Ms. Lovell oversaw a massive two-week project to truck the boulders 10 kilometers over bumpy winding roads to Columbia Hills State Park. Luckily, she says, none of them cracked in transit.

"The tribes were there to watch over," she said. "They did the appropriate blessings before. It was just a moment of pride and relief that they had come back to where they were. They looked like they belonged there more. And it was quite emotional for everyone."

Ms. Lovell says centuries after their creation, the petroglyphs remain enormously significant to northwest tribes.

"There'll be a panel out there that says, treat this as you would any other place of worship," said Gail Lovell.

That's the kind of education Bridget Whipple is hoping visitors will get. She's on the cultural heritage committee of the Confederated Tribes of the Warm Springs.

"You can sense spirituality around them when you go around the petroglyphs because they were used in prayer or they are used in prayer," said Bridget Whipple.

Ms. Whipple expects that the 200th anniversary of the explorations of Meriwether Lewis and William Clark will bring thousands of tourists through the Columbia River Gorge. She considers the petroglyphs a one of a kind opportunity for them to learn about northwest tribes.

"Because most of the people that will be part of it in telling the public, I'm sure they'll be expecting questions that one asking might think is a dumb question," she said. "But it will be good to get that dialogue going."

Park ranger Andy Kallinen walks to the long row of boulders arranged at the foot of a low rocky cliff face. Visitors here have an expansive view of steep mountains along a wide stretch of river. The new installation sits at the beginning of a preexisting path where rangers lead tours to the world famous image of "She Who Watches." Mr. Kallinen says visitors are awed by the huge stylized face chiseled high on the cliff wall, and he expects even more reverence at the new exhibit.

"We're still going to get some people who just happen upon it and go, 'wow.' Some of them just sit there and stare at them in silence for minutes and that's cool," he said.

Park rangers here are content to stay quiet when it comes to interpreting the imagery. Fellow ranger Fritz Osborn says out of respect for the tribes, they don't talk to tourists about what the petroglyphs may mean.

"They want something specific," said Fritz Osborn. "And we can't give them that. The meaning is sort of larger and broader than that. The person who made the petroglyph or pictograph is the one who had the original intent and knew the meaning. And in a way, to try to interpret that to something definitive really is to reduce it to something definitive. The scope of it is really beyond that." Restorers arranged the boulders as close to their original positions and configuration as they could, even facing a similar angle so the sunlight hits the images as it originally did. Each boulder lies on a gravel nest, so that within a season or two, they might come to look like they've been here all along.