Captain Meriwether Lewis wrote on April 7, 1805, that the party would probably pass down the Yellowstone River, which Indian information indicated watered one of the fairest portions of the continent. On the return journey, Captain Clark led a party of thirteen eastward to the Yellowstone River, including Sergeant Pryor; Privates Gibson, Bratton, Hall, Labich, Shannon, Shields, and Windsor; Toussaint Charbonneau; Sacagawea and her son Jean Baptiste, called Pomp; and Clark's servant York. Clark wrote that the Indian woman who had been of great service to him as a pilot through the country recommended a gap in the mountain farther south, which he would cross. The party entered the watershed of the Yellowstone River near present-day Bozeman Pass and reached the river on July 15, 1806. In eastern Montana, Paleo Indians arrived 11,500 years ago, with early remains found in the Lindsay area. Fur traders came in the mid-1700s because of the popularity of beaver hats. The 1803 Louisiana Purchase brought the area soon to be known as Montana into land owned by the United States, and French fur traders made the first known encounter with local tribes. Lewis and Clark and the Corps of Discovery entered Montana in 1805 and passed through again on their return in 1806. Steamboat traffic was introduced on the Missouri River in 1819, and Fort Union Trading Post was built near the confluence of the Yellowstone and Missouri Rivers in 1828, dominating the fur trade on the Upper Missouri River. The Fisk Wagon Trail was established in 1862 to connect the upper Midwest to Fort Benton, Montana became a territory in 1864, and the Battle of the Little Big Horn took place in 1876. The first train stopped in Glendive in 1881, Montana became a state in 1889, and in April 1909 the Bureau of Reclamation opened headgates for an irrigation diversion project that first delivered water to 67 farms in eastern Montana. In 1910 the homesteading boom was in full swing and agriculture replaced mining as Montana's top industry. An oil boom began in the Williston Basin in 1951, producing from fields in western North Dakota, southern Saskatchewan, and eastern Montana, and in 1969 the Northern Pacific, Great Northern, and Burlington railroads merged as Burlington Northern. From 2003 to 2006 came the 200 year anniversary of the Lewis and Clark Expedition.