Britain surrendered its claims over the vast territory named Indiana after its tribal inhabitants, under the 1778 treaty of peace ending the Revolutionary War. At the time the U.S. comprised the 13 former colonies that had constituted themselves as separate sovereign states united under the Articles of Confederation. Eleven years later, in 1789, those states dissolved the confederation and joined into one sovereign nation with a system of constitutional federalism.
With the passage of time and momentous events for another twelve years, in 1800 the Congress of the United States approved an organic act to govern the Indiana territory, based on the Northwest Ordinance model of territorial administration. By then political development in the territory was such that Congress determined there was no need for a period of territorial government with an appointed Governor and judges without an elected assembly, as contemplated by the Northwest Ordinance for Ohio.
Accordingly, the organic act for Indiana established a territorial legislature. Thereafter, through the anti-colonial mechanisms of the Northwest Ordinance the Indiana Territory eventually would be divided into the states of Indiana, Illinois, Wisconsin and parts of both Michigan and Minnesota.
The process for division of the territory into smaller jurisdictions was driven by the debate throughout the Indiana Territory over application of the anti-slavery prohibition in the organic act that originated in the Northwest Ordinance. The pro-slavery special interests had an ally in the Governor of the territory, but anti-slavery forces were tenacious. Impasse was resolved by a compromise allowing existing slavery to continue but prohibiting introduction of new slaves to the territory.
After the admission of Indiana in 1812, the next state to be formed from the original Indiana Territory would be Illinois, named after the dominant indigenous native tribe. The new Illinois Territory had achieved separation from Indiana in 1809, and an organic act was passed with the support of Indiana’s elected but non-voting Delegate in the U.S. House of Representatives. The Delegate’s support for the separation of Illinois was due in part to his sympathies as a resident of Dearborn, located in a region that also sought separation from Indiana, and that later would become part of Michigan.
By 1817 the Illinois territorial legislature petitioned to initiate the transition to statehood. However, the last census taken in 1810 counted the population at 12,282, far below the 60,000 person threshold that had been established as a standard criteria for statehood under the Northwest Ordinance.
At the time the average population represented by members of the House of Representatives was 35,000, making the 60,000 standard somewhat excessive. So when the Illinois petition was submitted to a Select Committee of the House, it was chaired by the Delegate from Illinois. The statehood enabling act enacted by Congress for Illinois required the population to be 40,000. It turned out the official population count came in at 40,258.
The statehood enabling act adopted by Congress also called for a constitutional convention, which completed its task in 23 days, leading to election of state officials and a Congressional delegation in September of 1818, followed by admission to the union in December of 1818, less than a year after the territorial legislature petitioned for statehood.