A Pawnee tribal delegation visited President Thomas Jefferson. In 1806 Lieutenant Zebulon Pike, Major G. C. Sibley, Major S. H. Long, among others, began visiting the Pawnee villages. Under pressure from Siouan tribes and European-American settlers, the Pawnee ceded territory to the United States government in treaties in 1818, 1825, 1833, 1848, 1857, and 1892. In 1857, they settled on the Pawnee Reservation along the Loup River in present-day Nance County, Nebraska, but maintained their traditional way of life. They were subjected to continual raids by Lakota from the north and west.