The end of the winter at Fort Mandan marked an important stage in the expedition; difficult and potentially dangerous as the route had so far been, all the men's efforts had been directed to reaching a point where other whites had ventured before them, on a route already mapped. From Fort Mandan on, they would enter country for which they had only Indian information and the conjectural maps based on that information and on geographical speculation.
All along the captains had distinguished between their "permanent party" and the others, boatmen and soldiers, who would return from some point up the Missouri. The heavy keelboat would become less useful as the river became shallower in its upper reaches, while the hired boatmen would be less necessary when the keelboat went back. They had designated Corporal Richard Warfington's squad from the start as the group that would return from some point during the first year carrying dispatches and specimens to President Jefferson. The original plan was that this return party would leave, probably in a pirogue, before the first winter; Jefferson would thus receive early word of the progress of the expedition, would have their first journals to peruse, and would receive their first plant, animal, and mineral specimens. Even if disaster later overtook the Corps of Discovery, something would be saved to add to knowledge of the West. The captains finally decided not to send this return party back before winter, but to wait for the following spring.
Among the items sent back were the journals completed to date; while there may still be room for some discussion here (see the Introduction to vol. 2), it seems clear that most of the daily journal material was Clark's, including the Field Notes and Codices A, B, and C. Lewis's Codex O, also sent back, is a collection of astronomical observations made during the first eleven months of the journey and "A Summary view of the Rivers and Creeks, which discharge thems[elves] into the Missouri. . . ." A more condensed, tabular list of rivers, creeks, and "remarkable places" by Clark is in Codex C; both men include lists of tributaries of the Missouri above Fort Mandan and of the Yellowstone, based on Indian information. There are also a number of miscellaneous documents that nearly repeat these summaries; they are discussed in the pages which follow. Lewis's and Clark's summaries form part 1. A list which identifies Lewis and Clark's points by their modern names is also a part of this section.
Some of Lewis and Clark's observations (such as astronomical notes and weather data) are dated and can be placed in the journals by date, as is done in this edition. Many of the other miscellaneous materials, however, cannot be dated with any precision, except that they clearly belong to the period ending with the departure from Fort Mandan. For this reason they appear together as a miscellany of observations covering the first phase of the expedition and sent back from Fort Mandan. One such item is an extensive separate document by Clark listing and describing Indian tribes east of the Rockies, his "Estimate of Eastern Indians." From this, supplemented by other journal material, Jefferson prepared "A Statistical View of the Indian Nations Inhabiting the Territory of Louisiana and the Countries Adjacent to its Northern and Western Boundaries," which he presented to Congress and which was published in 1806. Again miscellaneous documents duplicate this material and they are discussed below. The Indian material, along with a list identifying the tribes by modern designation, makes up part 2.
On the trip to Fort Mandan Lewis took extensive notes on the fauna and flora of the Missouri River valley. These he copied into special notebooks, Codices Q and R. The zoological material in Codex Q is placed in these volumes by date, as are astronomical and weather data. The botanical information from Codex R presents a different situation. The material is presented in the journal as a list, similar to the captains' summaries of rivers and creeks. Moreover, since many of the items are undated they appeared more appropriate for this section. Botanical specimens that were sent back from Fort Mandan with Warfington's party were eventually received by the American Philosophical Society and are listed in the Donation Book there. Part 3 contains the lists from Codex R and the Donation Book. Since so many of these plants are not mentioned in the captains' daily journals, a table has been added to match the lists and to give modern identifications of the plants as far as possible.
A list of mineral specimens sent back from Fort Mandan is also a part of the Donation Book, apparently a copy of a list prepared by the captains themselves, done by persons at the society. It appears as part 4. Part 5 is a section of miscellaneous items that were apparently drawn up at Fort Mandan, while part 6 is lists of Indian presents and "necessary stores" for the expedition from Codex C.