As early as 1866, the Osages were forced to cede tracts at the eastern and northern edges of the reservation. After the Civil War ended, the Osage lands were coveted as the largest and last reserve of good land in the eastern part of the state. The reservation had been established in 1825. When Kansas was admitted to the Union as a state in 1861, the Osage Indian reservation occupied a large tract of land near the southern border.

It was named in honor of Richard Montgomery, an American Revolutionary War general killed in 1775 while attempting to capture Quebec City, in Canada, after successfully capturing two forts and the city of Montreal. Montgomery County was established on February 26, 1867.

In 1854, the Kansas Territory was organized, then in 1861 Kansas became the 34th U.S. In 1803, most of the land for modern day Kansas was acquired by the United States from France as part of the 828,000 square mile Louisiana Purchase for 2.83 cents per acre. In 1802, Spain returned most of the land to France, but keeping title to about 7,500 square miles. In 1762, after the French and Indian War, France secretly ceded New France to Spain, per the Treaty of Fontainebleau. From the 16th century to 18th century, the Kingdom of France claimed ownership of large parts of North America. For many millennia, the Great Plains of North America was inhabited by nomadic Native Americans.

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