A few years ago, while filming a documentary on the Crow reservation in south-central Montana, I saw a New Yorker cartoon thumb-tacked to a door in the tribal offices. It showed two Indians sitting beside a fire, watching a rocket blast off into space. One says to the other: "Somebody told them we still have land on the Moon."

I forgot about that cartoon until a few months ago, when local newspapers began tracking the adventures of the Lewis and Clark Bicentennial Commemoration. The stories reported great excitement over the celebration in our nation’s thinly populated midsection, stories that were sometimes coupled with caveats written by native people, who tried to challenge perceptions about the Corps of Discovery. As I read these pieces, I reflected on words spoken several years ago by Gerard Baker, the Mandan-Hidatsa native who was named director of the National Park Service’s Lewis and Clark celebration.

"This will be a celebration of native people who made this expedition possible, a national celebration of their ancestors, their stories, their cultures," said Baker. "It’s long overdue."

So why is it, I am often asked by non-natives, that many Native Americans still feel such anger about this celebration? Why, while on a visit to Washington, D.C.,last week, was there a news commentary written by Mary Annette Pember, former president of the Native American Journalists Association, that began: "The Lewis and Clark Bicentennial Commemoration celebrates discovery by conquest, and as an American Indian, it sticks in my craw."

Pember explained that it sticks in her craw because the Corps of Discovery signaled the beginning of a century of trauma and genocide that ended on the frozen banks of a creek called Wounded Knee in December 1890. In effect, Pember asked, "What’s to celebrate?"

That’s a good question. When I was asked to speak at the Lewis and Clark Commemoration last month, I invited several judges and attorneys to join me in a panel discussion on "Compacts and Covenants: Two Hundred Years Downstream with the Doctrine of Discovery." My idea was to throw a bridge across the cultural gulf that continues to divide America.

Most of us are familiar with the Lewis and Clark adventure: Fifty-two men set out from Missouri in 1804, traveling West into the unknown; only one of them died. The official purpose of the mission was scientific. Fewer of us know that this was the 26th expedition of outsiders to reach the Mandan Villages on the upper Missouri River. Judging from the full auditorium in Bismarck, N.D., last month, fewer Americans know that the philosophy underlying the trip came from a medieval European pope justifying colonial expansion.

In1532, a brilliant thinker in Spain, Franciscus de Vitoria, delivered a lecture "On the Indians Lately Discovered in the Americas." Basing his arguments on the humanism of the Greeks, Vitoria argued that the native people living across the ocean possessed what he called "natural law rights," much like any free and rational people. As such, he said, they held title to their lands.

Vitoria’s lecture drew a stormy response from Pope Alexander, who declared that natives in the new lands were all savages and infidels. Under the pope’s Doctrine of Discovery, native people had a choice: They could be conquered, colonized and civilized by the agents of the church, or they could suffer the consequences.

Fast forward to Philadelphia, in 1787. There, our founding fathers enthusiastically embraced the 250-year-old Doctrine of Discovery. Furthermore, notes legal scholar Robert Williams, "... by denying self-determination to tribal peoples, the new republic found the Doctrine of Discovery to be the perfect instrument of empire."

Once ashore, the Doctrine of Discovery had many children. It spawned the odious Dawes Act of 1887, which abrogated dozens of treaties and opened tens of millions of acres of the American West to outright theft by Congress. It gave birth to the Religious Crimes Code which outlawed religious freedom to native people, and in our time, it spawned the Termination Era of the 1950s, a scandalous campaign that sought to disband Indian tribes altogether.

Thankfully, this last effort failed. But to America’s first citizens — and to journalist Mary Annette Pember — these episodes serve as a reminder that the Doctrine of Discovery is still very much with us. A rocket blasting off to a new frontier carries different symbolic meaning to people still fighting to recover their "inalienable rights."

Paul VanDevelder is a contributor to Writers on the Range, a service of High Country News (hcn.org). He is the author of the recently published, Coyote Warrior: One Man, Three Tribes, and the Trial that Forged a Nation. He lives in Corvallis, Oregon.