The area of Michigan was part of the original territory of the United States, being part of lands ceded by four states to the United States and designated in 1787 as the "Territory northwest of the River Ohio." Michigan Territory was organized on June 30, 1805, from the northeastern part of Indiana Territory, and included all of the Lower Peninsula, the eastern part of the Upper Peninsula, a small strip of northern Indiana, and a portion of northwestern Ohio that was later contested. In 1818, when Illinois was admitted as a state, all of the remainder of Illinois Territory was added to Michigan Territory, including almost all of present-day Wisconsin, part of Minnesota, and the western part of the Upper Peninsula; at the same time, the central portion of the Upper Peninsula and eastern Wisconsin were added from the former Indiana Territory. In 1834, Michigan Territory was enlarged from part of Missouri Territory, including all of present-day Iowa, the remainder of Minnesota, and the eastern part of North Dakota and South Dakota. Michigan was reduced with the organization of Wisconsin Territory and the cession of the Toledo Strip to Ohio in 1836. As a compromise for the cession of territory to Ohio, Michigan Territory retained all of the Upper Peninsula when Wisconsin Territory was organized, resulting in a boundary generally the same as the present state. Michigan was admitted to the Union on January 26, 1837, as the 26th state.