MISSOULA, Mont. (AP) - The next great bicentennial is upon us.

No sooner did Meriwether Lewis and William Clark amble off into the sunrise than along came David Thompson, slowly making his way down from Canada.

Thompson was a London-born explorer, surveyor and trader for the Hudson's Bay Co. and North West Co. He spent most of five years prowling the Columbia River basin of the Rocky Mountains starting in 1807 - the year after Lewis and Clark returned home from their western expedition.

A monument to David Thompson is one of 56 state historic sites in North Dakota, though it has drawn few visitors on the banks of the Souris River near Verendrye. Thompson mapped the area in 1797 and 1798, historians say.

Thompson is more the hero in Canada than in the U.S. - he was, after all, British and spent most of his time north of the 49th parallel. But his path sometimes intersected with President Thomas Jefferson's Corps of Discovery.

Two hundred years later, they're crossing paths again.

"The way the Lewis and Clark bicentennial elevated the general awareness of history and details of natural history and politics and landscape that sort of make our place what it is was really remarkable," Jack Nisbet said recently in Lolo. "It's really one of the most successful history events I think I've ever imagined.

"Thompson's bicentennial is different because he's quite a different guy. But he does bump into them, especially Thomas Jefferson, over and over again during his life."

Nisbet presented a slide show and talk about Thompson's life to some 60 history buffs at the Lolo Community Center. The program, sponsored by the Montana Committee for the Humanities Speaker's Bureau, was hosted by the Travelers' Rest Chapter of the Lewis and Clark Trail Heritage Foundation.

A teacher, naturalist and writer from Spokane, Wash., Nisbet has written five books. Two of them were on Thompson: "The Mapmaker's Eye: David Thompson on the Columbia Plateau" and "Sources of the River."

Thompson first reached Montana in 1808, but his bicentennial celebration has indefinite parameters. The North American David Thompson Bicentennials last the three years from 2007 to 2009. Regional commemorations are planned for the three years following that.

Nisbet looks at it in even broader terms.

"It's been going on for 22 years as an explorer and it's got five more to go," he said. "Then as a surveyor it's got another 30 to go after that. So he's in it for the long haul."

Chances are, the attention will root out some of the same kind of revelations the 200th anniversary bash for Lewis and Clark did, particularly when it comes to understanding the native people they all encountered.

Thompson far outstripped the Americans in that department. He spent years among the Indians of the West, married a Cree, and consistently put his life and livelihood in their hands.

Lewis and Clark were on a 2½-year military expedition, out in part to annex land and the people who lived on it in the name of the United States.

"That was incredibly different than the commercial aspects of David Thompson's world," said Nisbet. "It's what makes their stories so different."

Thompson called the Clark Fork River, from its head in Montana to the Columbia, the "Salish drainage."

"That's because Salish-speaking people lived on it, and they all spoke the same Salish language. Now we would say Flathead, Pend O'Reille, Kalispel," he said.

Thompson's mapmaking was prodigious, his travels extensive, his observations meticulous, his writings voluminous. In the Columbia plateau, he established trading posts he named Kootenae House at Lake Windemere, British Columbia; Kullyspell House near Hope, Idaho; Saleesh House at Thompson Falls.

When he was 29, he married a 13-year-old Cree, Charlotte Small, with whom he had 13 children. Charlotte and a couple of the kids were with him when he made his first venture over the Rockies in 1807.

Charlotte and David stayed together for 57 years. They died three months apart in 1857, when Thompson was 87 years old.