Wagons West: The Epic Story of America's Overland Trails. By Frank McLynn. Grove Press. 528 pages. $32.50.

Historian Frank McLynn has written a graphic, meticulously researched account of the men, women and children who ventured from the Midwest to the Pacific on the Oregon and California trails from 1840 to 1849 and the hardships that confronted them almost daily, including rain or heat, disease, accidents and death.

"The exhaustion and fatigue of the daily treks, the dangers anticipated from Indians and the uncertainty of supplies of food, water and forage exacerbated nervous tension," McLynn notes. "Friction was unavoidable and grumblers and malcontents could always find a focus in other people for their discontents."

Then, as occurs often in the book, McLynn quotes from an emigrant's diary: "Alonzo Delano had pithy expressions for both cause and effect: on the exhaustion -- 'a hyena might have tugged at my toes with awaking me'; and on the myriad frivolous collisions with one's fellows -- 'a mean streak will come out on the plains.' "

After an opening chapter summarizing the early settlement and exploration of the West, when "mountain men" -- Kit Carson, Jim Bridger, Jedediah Smith and others -- and missionaries like Dr. Marcus Whitman were the only significant white American presence west of the Mississippi except in Texas, McLynn reports in detail on the great emigrations that began in 1840, touched off by economic depression, plummeting land and farm-produce prices and "the dream of escape to the open frontier, where you can change occupation, lifestyle or even identity."

Chapter by chapter, McLynn traces the wagon trains' trials, suffering and triumphs, beginning with John Bidwell, 22, described as a "restless spirit," who was instrumental in forming and leading what McLynn says was "the first proper emigrant crossing to California" in 1841, to the Donner Party's terrible entrapment in the snow of the High Sierras in the winter of 1846-1847. The final chapter, "Saints and Sinners," recounts the Mormons' epochal 1846-1848 trek from Nauvoo, Ill., to the Great Salt Lake.

Throughout, McLynn provides intimate, perceptive insights into that time. Noting the increasing presence of women, but the lack of female diaries, probably because the women had too many family responsibilities, McLynn quotes from the diary of James Clyman, who wrote while crossing the plains in 1844 during a depressing period of heavy rainfall: "I thought I never saw more determined resolution even among the men than most of the female part of our company exhibited. ... There was one young lady who showed herself worthy of the bravest undaunted pioneer of the West. ... She nursed a fire, ... held an umbrella over the fire and her skillet with the greatest composure for near two hours and baked bread enough to give us a plentiful supper."

McLynn's summing up of the Donner tragedy could apply as a metaphor for the intrepid trek west before the discovery of gold in California in 1848 triggered a massive get-rich-quick emigration wave.

"It is a classic tale of heroes and villains. ... The Donner tragedy illustrates a perennial truth. There are almost no depths of infamy to which human beings cannot sink, but they are also capable of godlike courage, nobility, and self-sacrifice."

Edwin O. Guthman, a professor at the University of Southern California school of journalism, was editor of The Philadelphia Inquirer from 1977 to 1987. Before that, he worked at the Los Angeles Times, The Seattle Times and the Seattle Star. He was press secretary to Robert F. Kennedy when R.F.K. was U. S. attorney general and when he first ran for the U.S. Senate. He has edited and written several books, including We Band of Brothers in 1971.