The Indiana Territory was created by an Act of Congress and signed into law by President John Adams on May 7, 1800, effective on July 4. It was the first new territory created from lands of the Northwest Territory, which had been organized in 1787 by the Northwest Ordinance. The territory originally contained approximately 259,824 square miles (430,000 km2) of land, but twice decreased in size as it was further subdivided into new territories.
The territory was first governed by William Henry Harrison who oversaw the negotiation with the native inhabitant to open up large parts of the territory to settlement. In 1810 a popularly elected government was established as the territory continued grow in population and develop a very basic road network, government, and education system. At the outbreak of Tecumseh's War, the territory was on the front line of battle and Harrison led a military force in the opening hostilities at the Battle of Tippecanoe, and then in the subsequent invasion of Canada during the War of 1812. Thomas Posey was appointed to the vacant governorship, but the opposition party, led by Congressman Jonathan Jennings, had dominance in the territorial affairs for its remaining years and began pressing for statehood. In June 1816, a constitutional convention was held and a state government was formed. The territory was dissolved on November 7, 1816, by an act of Congress granting statehood to Indiana.