Illinois' fertile prairies drew French trader Louis Jolliet and Father Jacques Marquette during their exploration of the Mississippi and Illinois Rivers in 1673. France claimed the region until 1763, when it surrendered it to Great Britain by the Treaty of Paris. During the American Revolution, George Rogers Clark captured Kaskaskia in a bloodless victory for the Commonwealth of Virginia, and Illinois became a county of Virginia. The area was ceded to the United States in 1784 and then became part of the Northwest Territory and later the Indiana and Illinois Territories. On December 3, 1818, Illinois entered the Union as the 21st state. Above Hamilton, the lower rapids of the Mississippi River obstructed steamboat navigation. In 1820, the steamboat Western Engineer reached the foot of the rapids, and three years later the Virginia passed through the swift, shallow water. In the late 1830's, Lieutenant Robert E. Lee supervised drilling and blasting to widen and deepen the river channel, but when that effort proved too costly and ineffective, work began in 1866 on an independent canal around the western side of the rapids. Between the Mississippi and Illinois Rivers, Highway 136 passes through the military tract, land used as bounty land for veterans of the War of 1812, and near places including Warsaw, site of Fort Edwards of 1814, Nauvoo, Mormon city of the 1840's, and Dickson Mounds, an ancient Indian burial site near the Illinois River.