 This situation remained in effect for decades because as the free states of Michigan, Wisconsin, and Iowa were admitted to the Union, the new slave states of Arkansas, Florida, and Texas were also admitted.When the Republic of Texas joined the United States in 1845 as a slave state, it was required to cede all of its claimed land north of the 36°30′ latitude to the Federal Government.Over the following half-century, this land became parts of Kansas, Colorado, New Mexico, and Oklahoma.