On June 4, 1804, a keelboat and two pirogues carrying the Corps of Discovery passed through the Jefferson City area on their way up the Missouri River, across the Rocky Mountains, and toward the Pacific Ocean during the twenty-second day of the Lewis and Clark Expedition's two-year, four-month journey. Having already traveled more than 145 miles from their winter encampment at the River DuBois in present-day Illinois, the party still faced 3,855 miles to the western edge of the continent. As they passed the future site of Missouri's capital, the detachment included 45 men, among them the Captain's Mess, as well as 24 American soldiers on the keelboat under three sergeants, eight French-Canadian engagés on the red pirogue, and six privates and a corporal on the white pirogue. After leaving a three-day camp at the mouth of the Osage River on June 3, where they had taken measurements and scientific observations, they moved to the mouth of the Moreau River, where William Clark heard an unfamiliar bird and named nearby Nightingale Creek for it, while also recording signs that Indian war parties had crossed there, apparently confirming reports that Sauk and Fox war parties had crossed to fight the Osage. The expedition then continued past Cedar Island and Cedar Creek, where the 55-foot keelboat's mast broke after becoming entangled in a sycamore over the channel, even as the men admired the fine land and rich timber along the river. Near the end of a 17.5-mile day they passed a creek Clark called Zoncar, later pronounced Joncar, a French word meaning rush, fitting the floodplain vegetation there. After another three miles, Clark went ashore to investigate reports of lead at a large hill ahead. Crossing a rush-covered bottom and chest-high nettles, he climbed Lead Mine Hill, estimated it at 170 feet high, found no lead, saw a six-foot Indian mound likely dating to the Late Woodland Period, ca. 400-900 A.D., and observed a hundred acres of dead timber. He then descended to a semicircle of extensive shelter caves and reached Sugar Loaf Rock, from which he could see the river for 20 or 30 miles upstream, before going down to the camp where the party ended the day and where the hunters returned with seven deer.