The Kansas–Nebraska Act becomes law (replacing the Missouri Compromise of 1820) on May 30, 1854, creating the Kansas Territory and the Nebraska Territory, west of the State of Missouri and the State of Iowa.

The Kansas–Nebraska Act also establishes that these two new Territories will decide either to allow or disallow slavery, depending on balloting by their residents (these areas would have been strictly "free territory" under the Missouri Compromise, which allowed slavery in the State of Missouri but disallowed it in any other new state north of latitude 36° 30', which forms most of the southern boundary of Missouri.

This prohibition of slavery extends all the way from the western boundary of Missouri to the Pacific Ocean).