Human history in what is now Chaffee County long predated its inclusion in the United States through the 1803 Louisiana Purchase, as native Utes and Comanches used paths that later became modern roads and trails. The Utes, the oldest continuous residents of Colorado, lived seasonally by dispersing in family groups from spring to fall to hunt and gather food, then gathering in winter around central camps, especially in the Gunnison Valley near Montrose and in the San Luis Valley. Their way of life changed significantly after contact with European explorers, particularly the Spanish, whose first recorded peaceful trade with the Utes came in 1626; horses became the most important trade item and enabled Ute buffalo hunting on the eastern slope of the Rockies, with local bands traveling between the San Luis Valley and South Park through present-day Chaffee County along what became known as Ute Trail. Spanish presence in the Upper Arkansas River Valley was recorded as early as 1626, though Spain's official exploration of southwest Colorado began about 150 years later, and in 1779 General Juan Bautista de Anza's campaign against the Comanche produced the first recorded crossing of Poncha Pass. Because the southern boundary of the Louisiana Purchase with New Spain remained unclear, Lieutenant Zebulon Pike was sent west in 1806 to investigate the United States' new southwestern border, bringing him into the Upper Arkansas Valley and to the Arkansas River. After earlier exploring the Mississippi River to its head and then being ordered to build relations with native peoples and learn the Louisiana Territory's southwestern boundary, Pike reached the Arkansas River near present-day Pueblo in November 1806, intending to follow it to its headwaters and then return along the Red River. After failing to climb the peak later named for him, he turned into South Park, crossed Trout Creek Pass above present-day Buena Vista, and entered a broad river valley that he mistakenly believed was the Red River rather than the Arkansas. With provisions dangerously low and his men unprepared for winter, Pike wrote on December 24 that they had not eaten for several days until advance members of the party killed buffalo, after which the group reunited and camped on the north bank of the Arkansas at the mouth of Squaw Creek. Stormy weather kept them in camp on Christmas Day to repair equipment and replenish food, and Pike recorded the severe hardship of cold, hunger, inadequate clothing, and sleeping on snow or wet ground. On December 26 they camped at Big Bend near present-day Salida, then continued downstream until recognizing their mistake and turning south in search of the Red River. Early in 1807 they crossed into the San Luis Valley at the Great Sand Dunes and built a log stockade near present-day La Jara, where Pike was seized by the Spanish, questioned as a suspected spy, and escorted with his men back to U.S. territory through Texas and Louisiana; many of his notes were confiscated, so his later book and reports were written largely from memory.