The Corps reached the mouth of the Musselshell at 11 A.M. on May 20, 1805, halted for the remainder of the day, and produced one of the most fully documented confluences of the entire ascent. All five active journalists wrote at length, and their convergence on the same fixed point — 222 yards of Missouri meeting 110 yards of greenish-yellow tributary — offers an unusually clean test of how each narrator handled identical raw material.
The Same Numbers, Different Hands
Lewis, Clark, Ordway, and Gass all record the Missouri at 222 yards and the Musselshell at 110, and all four give the latitude as 47° 00′ 24″ North. Whitehouse alone garbles the figure, writing
found the latitude 47°, 24′ North
— dropping the minutes of arc entirely and producing a position roughly twenty-four miles too far north. The error is characteristic of Whitehouse’s working method on this date: his entry otherwise tracks Ordway’s almost phrase by phrase (the caught beaver, the cottonwood bottom, the pitch pine and cedar hills, the 11 o’clock arrival), but where Ordway gives the distance from the Missouri’s mouth as 2270 miles, Whitehouse writes 2271, and where Ordway logs seven miles for the day, Whitehouse logs six. The Whitehouse-from-Ordway pattern is visible here in miniature, with small transcription drift accumulating at every numerical waypoint.
Gass, by contrast, compresses the same material into roughly a hundred words and gets every figure right, including the detail — absent from Ordway and Whitehouse — that the Musselshell’s mouth lies
660 miles above Fort Mandan
. Gass alone anchors the distance to the winter post rather than to the Missouri’s mouth, a choice that reflects the working geography of a man who had spent five months at Fort Mandan and reckoned upstream from there.
Lewis the Geographer, Clark the Surveyor
Lewis writes by far the longest entry and is the only narrator to interrogate the Hidatsa intelligence about the river. He notes that the Minnetares had told the Corps to expect
a well timbered country in the neighbourhood of it’s mouth
and then carefully qualifies the claim, observing that
nine tenths of the country being wholy destitute of timber of any kind
. The cottonwood is confined to the bottoms; the upland “timber” the Hidatsa described is, in Lewis’s revised reading, only scrubby pine and dwarf cedar on the highest ridges. This is Lewis using direct observation to recalibrate received geography — the same epistemic posture that will mark his later encounters with Hidatsa-derived information about the Great Falls and the Three Forks.
Clark, characteristically, did the measuring. He records the meridian altitude as
59° 50′ 0″ back observation
— the only narrator to preserve the actual instrument reading behind the latitude. He also walks the country, kills two deer and an elk, and notes a small tributary entering the Musselshell five miles above its mouth, a feature Ordway repeats but Lewis omits.
Blowing Fly Creek
The naming of Blowing Fly Creek, four miles below the Musselshell, is preserved by every narrator except Gass, who mentions only an unnamed creek on the south side. Lewis gives the fullest etymology:
they infest our meat while roasting or boiling, and we are obliged to brush them off our provision as we eat
. Ordway and Clark use nearly identical phrasing about brushing the flies from food, suggesting either a shared evening conversation or one journal informing another. The detail is small but valuable — it is the kind of camp-life observation that vanishes from official cartography but survives because four men independently thought it worth recording.
The hunters’ tally also varies meaningfully across narrators. Whitehouse alone provides a full count:
Eight Deer 4 Elk one woolf
. Clark records his personal kills and a vaguer collective figure; Lewis defers the hunters’ report to a single summary sentence; Gass omits the hunt entirely. The pattern holds across the expedition — Whitehouse, despite his copying habits and arithmetic slips, is often the most reliable accountant of game.
