Dennis McNally was raised in a military family before graduating high school in Maine. He attended St. Lawrence University and then received his Masters and Ph.D. in American History at the University of Massachusetts, Amherst. His dissertation, a biography of Jack Kerouac, was published by Random House in 1979 as Desolate Angel: Jack Kerouac, the Beat Generation, and America.

In pursuit of his next book, a history of the Grateful Dead, he settled in San Francisco in 1977, where he has made his home ever since. He began work on the Dead history in 1980 at the invitation of Jerry Garcia, and in 1984 the Dead hired him as their publicist. He continues to hold this position. The obligations of the job required him to put the book on hold, and he only resumed it in 1997, after the death of Garcia. A Long Strange Trip: The History of the Grateful Dead, was published in 2002.