Sources for the main divisions of this book are noted below in the general
bibliography, which is arranged topically. Additional, more specific refer-
ences follow, arranged by chapter and topic. There is, of course, some
overlapping. The intent is not to furnish data for scholars but to suggest
to interested readers avenues to additional information.

The unpublished sources used in preparing this account include a letter,
October 7, 1809, of Pierre Menard to Langlois, photostat furnished by the
Missouri Historical Society; and Cyrus Shepard's "Journal of a Trip across
the Plains in 1834," microfilm furnished through the courtesy of the Coe
Collection, Yale University Library.

At the Henry E. Huntington Library, San Marino, California, I was priv-
ileged to peruse William Marshall Anderson's "Notes of Remembrance
Taken on a Tour of the Rocky Mountains March 11, 1834 to September
29, 1834," and the manuscript diaries of Elkanah Walker and Mary R.
Walker. The diaries of Mary Walker were published, with deletions, by the
University of Montana in 1932 in the Sources of Northwest History, num-
ber 15. At the Huntington Library also, I was able to use a "script, pre-
pared by C. J. Brosnan, of Francis Ermatinger "Correspondence, 1823-
1853," finding especially useful his letters to his brother Edward dated
March 11, 1836, March 16 and June 1, 1837, and March 19, 1838.

The Wyles Collection at the library of the University of California at
Santa Barbara contains microcards of nearly every item listed in Henry Wagner's
and Charles Camp The Plains and the Rockies, A Bibliography of
Original Narratives of Travel and Adventure, 1800-1865. These reproduc-
tions made readily available many rare accounts I could not otherwise have
studied.

I learned of the Menard letter cited above from Richard Oglesby. Its
colloquial French and difficult penmanship were deciphered for me by
Denise Miller and Andrée Schlemmer. Dale L. Morgan answered various
questions with his usual unfailing courtesy and exhaustive care. George R.
Stewart and Joe Backus first and later Tom May were delightful traveling
companions along various sections of the trail, trips most pleasantly broken
by the hospitality of Sue and Charles Beck at their ranch near Dubois,
Wyoming. Leith Moreland helped with the maps; the data for those dealing
with the Great Lakes and Upper Mississippi were furnished in large part by
the Minnesota Historical Society.

My wife Mildred typed the finished copy of the manuscript; more impor-
tantly, she regenerated buoyancy when at times I began to sag.

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