David Galloway's "Tamsen" should stroll away with all of the year's prizes for the best historical novel of 1983.

Tamsen Donner is the wife of George Donner, a man who has "carved homesteads from the forests as casually as idle men whittled a stick," and who, in April 1846, sets out from Springfield, Ill., with his extensive family and all their worldly wealth on the treacherous journey across the continent to California. For George Donner, now in his sixties, this is in many ways a "crusade against death itself." For Tamsen, it is a test of courage and endurance whose dangers far exceed the blackest terrors of nightmare. And for Americans ever since, the true story of the Donner party has been one of the most harrowing tragedies among the tales of our nation's westward growth.

They set out happily from Springfield, their wagons weighted with food, tools, clothing, bolts of cloth, and a precious store of gold coins, and accompanied by a small herd of milch cows and oxen and a number of friends and hired hands who, lacking property of their own, are willing to work their hard way across the land. If their wagons are bursting with goods, their hearts and minds are bursting with pride at their own daring and wonder at the size of their adventure.

But the westward path, deeply rutted from the passage of other caravans before them, is even harder than expected. As they move painfully on, the harsh land wears them down, blinding some of them with biting alkali dust, sand, salt winds, and grinding away the stamina of men and beasts with exhausting labor. They press on, "more and more resembling a routed army." Even so, they are a competent group, "a rich and varied nucleus for the germ of civilization they were conveying to the Pacific." Life goes on, and a single day on the trail sees a birth, a death and a marriage. "The rhythms of life," Tamsen Donner writes in her journal, "continue to regulate themselves as they are wont to do elsewhere."

But as the weeks pass, and then the months, they fall dangerously behind schedule. When they reach the western mountains at last, they are even more exhausted from their six months on the trail, their group numbers only 79 men, women and children, their stores have run alarmingly low, and their worn-out animals are nearly useless. Then, at the end of October, near Prosser Creek in the Sierra Nevadas, just north of present-day Lake Tahoe, the Donner party is trapped by a savage early-winter snowstorm.

What follows is hair-raising, a relentless catalogue of calamities that grows so terrible, from day to day and from page to page, that we are convinced that the cruelty of circumstances and character is--must be--exhausted. It is not. The avalanche of misfortune tumbles only more rapidly through the final pages of the book, the final weeks and months in the mountains, and the reader lives through them wide-eyed and breathless. Near the end, facing certain starvation, the remaining survivors must face "the sole and awful alternative," and they turn to the bodies of their dead companions for nourishment. And yet, after even this, still greater shock and horror await, and the reader who can finish this book without feeling his hands trembling on the page simply has not been paying attention.

Rising far above the horrors of the struggle, however, is the glowing character of Tamsen Donner. This is certainly one of the most memorable portrayals ever set on paper, a figure of breathtaking strength, courage and determination, the quintessential American pioneer woman, who keeps her own fears clenched tightly within as she strives to see her husband and children successfully through their ordeal. She is a wonderful person to know.

But Galloway handles dozens of other characters here with equal brilliance. His narrative prose is a tribute to the language and his recreation of Tamsen's journal a tour-de-force of characterization and style. This book does not have a sentence in it that is dull or useless, not a page without drama, not a line of dialogue without its own authentic voice, not a character without a unique profile.

Galloway--born in Memphis, Tenn., and holding the chair of American Studies at Ruhr University in West Germany--has mastered a staggering amount of research, but he presents it all with stunning dramatic effect in this richly detailed novel. He manages also to keep the westward trek of the Donner party in historical perspective with reminders of the nation's growth through threatened wars in Texas and California at the time, and the novel thus expands far beyond its own story, becoming an epic retelling of the archetypal American tale.