When President Thomas Jefferson went ahead with the Louisiana Purchase, he wasn't entirely sure what was on the land he was buying, or whether the purchase was even constitutional. Ultimately, the Louisiana Purchase encompassed all or part of 15 current US states and two Canadian provinces, including Arkansas, Missouri, Iowa, Oklahoma, Kansas, Nebraska, parts of Minnesota that were west of the Mississippi River, most of North Dakota, nearly all of South Dakota, northeastern New Mexico, Northern Texas, the portions of Montana, Wyoming, and Colorado east of the Continental Divide, and Louisiana west of the Mississippi River, including the city of New Orleans. In addition, the Purchase contained small portions of land that would eventually become part of the Canadian provinces of Alberta and Saskatchewan. The purchase, which immediately doubled the size of the United States at the time, still comprises around 23 percent of current American territory. With so much new territory to carve into states, the balance of Congressional power became a hot topic in the decade after the purchase, especially when the people of Missouri sought to be admitted to the Union in 1819 with slavery being legal in the new state. While Congress was dealing with that, Alabama was admitted in December 1819, creating an equal number of free states and slave states. Thus, allowing Missouri to enter the Union as a slave state would disrupt the balance. The Senate ultimately got around this issue by establishing what became known as the Missouri Compromise. Legislation was passed that admitted Maine as a free state, thus balancing the number once Missouri joined as a slave state. Moreover, slavery would be excluded from the Missouri Territory north of the parallel 36 30 north, which was the Southern border of Missouri itself.