My life can get so hectic that I nearly forget who I am. I was driving pell mell from Fargo to Bismarck on Tuesday night when it suddenly struck me that it was Meriwether Lewis's 235th birthday. Jefferson's protege was born on Aug. 18, 1774, within sight of Monticello.

There was a time in my life, and not long ago, when I lived and breathed Lewis and Clark. Now that remarkable adventure (1803-06) has slipped to the second tier in my cluttered-up garage or attic of a mind. I felt a twinge of sadness and shame that I have let Lewis and Clark slip a little. It's like very nearly forgetting your best friend's birthday.

The '60s poet Rod McKuen wrote, "The mind is such a junkyard. It remembers candy bars but not the Gettysburg Address, Frank Sinatra's middle name but not the day your best friend died." Indeed. I can remember a couple dozen plotlines of "The Andy Griffith Show" and even "Charlie's Angels," but this morning, at dawn, I was trying to remember the Labors of Hercules and I couldn't get past four. That's terribly saddening. But it also tells you something about the power of television.

At any rate, happy birthday, Meriwether Lewis. Not that he would be glad to be so greeted. Though American mythology remembers Lewis and Clark as cheerful, more or less interchangeable, heroes in buckskins, they were actually remarkably different men. Clark fits the stereotype pretty well, but his friend Lewis was a tightly wound, self-critical, brooding, often melancholic man who took himself, his transcontinental mission and life very seriously. During the two years he lived with the immortal Jefferson in the White House prior to his expedition, the cheerful, even-tempered and Pollyanna-esque president noticed what he called "sensible depressions of spirit." He also noticed that Lewis drank, sometimes to excess.

That, at least, was Jefferson's retrospective assessment in 1813, four years after his protege committed suicide.

Yes, suicide. I remember the moment when I first learned that the leader of the Lewis and Clark Expedition, the Neil Armstrong or John Glenn of his time, killed himself just three years after his return to civilization, after leading an amazingly successful 7,689-mile scientific expedition from St. Louis to the Pacific Ocean and back again, by way of our own Missouri River. He was 35 at the time of his death. He put a gun to his head and another to his abdomen at a lonely trailside inn in Tennessee. When I read that for the first time, in a book by David Freeman Hawke, I was in the office of the late, great Everett C. Albers, director of the North Dakota Humanities Council. "Did you know Lewis committed suicide in 1809?" I asked. Ev, who believed that the humanities are the elixir, the sorcerer's stone, the key to a complete and satisfying life, said, "No. Why did he do it?"

I have been trying to answer that question for the last 25 years. And not with much success. Suicide is always a profound mystery, even when the perpetrator and victim leaves a suicide note, which Lewis did not. I have hunches about Lewis, based on repeated and thorough sifting of the evidence, reading and rereadings of the large and growing literature on the subject, including Lewis's journals, endless meditation, research into the troubled returns of other explorers, including the fascinating contemporary case of the second man on the moon, Edwin "Buzz" Aldrin, and careful readings of case studies of the suicide phenomenon, beginning with John Donne's "Biathanatos" (the first-ever defense of suicide) and ending with the Johns Hopkins psychology professor Kay Redfield Jamison, whose book "Night Falls Fast: Understanding Suicide" has a chapter on Lewis saying that he is just the sort of driven, high-strung, self-castigating man who fits the profile.

In the end, the survivors never really know why anyone committed suicide, including someone they have known intimately for a lifetime. The mystery abides, deepens, perplexes and eats away at one's sense of the rightness of things. For most of the history of Christianity, definitively since St. Augustine's definitive "City of God" (A.D. 410), suicide has been regarded as a sin and a crime. I'm with John Donne: judgment is easy, understanding hard, almost impossible, and that is in our interest always to be charitable about something so intensely personal and inexplicable. I know this, too: That a suicide, any suicide, is like stone dropped into a very wide pond, creating a permanent (multi-dimensional) ripple action that gnaws at all the survivors and creates a crisis of meaning and identity for everyone who knew the person in question.

I have been writing about this as if Lewis's suicide, though ultimately a mystery, is an unquestioned fact of American history. That is not quite so. Though Lewis's two closest friends, Thomas Jefferson and William Clark, were shocked but not surprised when they heard the news in October 1809, and though all the evidence we have points to suicide, a dedicated cadre of diehards believes - hook, line and sinker - that Lewis was murdered on the Natchez Trace (murderer unknown) and that some sort of conspiracy was undertaken by those around Lewis to call it suicide instead. The murder theorists are loud and fiercely determined, and they are trying to get poor Lewis exhumed so that forensic experts can examine the skull. This has a kind of "second gunman, grassy knoll" feel to it. My hope is that the National Park Service, which maintains the burial site at Hohenwald, Tenn., will continue to refuse to extricate Lewis's bones.

My own deep prejudice is that documents, near eyewitness accounts and historical analysis are a better tool than shovels in making sense of the richness and complexities of Meriwether Lewis.

Lewis celebrated (well, observed) his 31st birthday on the Idaho-Montana border near Dillon, Mont., on Aug. 18, 1805, not long after he bestrode the source waters of the "mighty and heretofore deemed endless Missouri River." After acknowledging that he had lived about half the time he expected to dwell in "this sublunary world," Lewis fell into dark self-reflection. "I reflected," he wrote, "that I had as yet done but little, very little indeed, to further the happiness of the human race, or to advance the information of the succeeding generation. I viewed with regret the many hours I have spent in indolence, and now sorely feel the want of that information which those hours would have given me had they been judiciously expended."

Well, I can certainly relate to that. I find myself in the midst of a much less articulate, but similarly self-critical, look in the mirror about once a week, and I'm now way beyond the halfway point of my time in "the sublunary world."

Even so, like Lewis, I always conclude my self-flagellation with resolute optimism. Said Lewis, "I resolved in future, to redouble my exertions and at least endeavor to promote those two primary objects of human existence, by giving them the aid of that portion of talents which nature and fortune have bestowed on me; or in future, to live for mankind, as I have heretofore lived for myself."

Rest in peace, Capt. Lewis.

(Clay Jenkinson can be reached at Jeffysage@;aol.com.)