The expedition explored for about three weeks below Natchitoches, in present-day State of Louisiana, which was the last American settlement on the Red River. This is where John Sibley, Dr. John Sibley, the American Indian Agent, was located, and he outfitted the Expedition in June of 1806 with additional trade goods, so that the party could trade for horses from the Wichita Indians when they got far upriver.
Another military contingent was added to the Expedition at this point, and that brought the total size of the Grand Excursion to the Southwest up to fifty individuals, which made it an even larger expedition than the Lewis and Clark Expedition. In fact, it's the largest American exploring party of the age. It included several French guides, who were going to act as guides to the Wichita villages, and it would ultimately include two or three Caddo Indian guides as well.
So on June the second of 1806 the party left Natchitoches fully outfitted, ready to explore to the headwaters of the Red River. It immediately confronted an enormous and what seemed to be an almost insurmountable problem in the form of a log jam that was called the Great Raft. This Great Raft was perhaps as much as a thousand years old, and it stretched for a hundred miles up the river. In order to get around it, the Expedition, which now consisted of seven boats, had to detour eastward around the Red River, through a creation of the Red River which at the time was known as the Great Swamp. It is considered by ecologists today to have been a swamp land that would have been easily the equal of today's Okefenokee Swamp in Georgia. It took the Expedition almost two and a half weeks of what Freeman called "incessant toil, fatigue and uncertainty," to work their way through the Great Swamp and gain the Red River once again above the head of the Great Raft.
Peter Custis, meanwhile, was having a field day cataloging botanical specimens and observing neotropical wildlife. It was a paradise for him, but for the rest of the party this was evidently a real nightmare, trying to get around this Raft. They finally managed to do it in early July of 1806. At that point they stopped at an Indian village of Alabama-Coushattas on the river, where the Caddo Indians, who lived about thirty miles to the west, trooped over and spent four or five days with the explorers, and Freeman went through the classic Jeffersonian presentation to the Caddos and the Alabama-Coushattas about how these Indians, who had formerly been Spanish Indians, now had a new Great Father in Washington, and so forth.
The Caddos told the American explorers that there was already a Spanish army paralleling their movements in the hills about twenty miles to the west of them, and that this army was led by, as the Caddo chief described it, a "very bad man who cut down the American flag that was flying in the Caddo village," and was preparing to violently stop the American expedition. And so the Freeman and Custis party at this point must have been wondering whether or not they were going to live through whatever the next month of exploring would bring.