MISSOURI COMPROMISE. The parallel of 36°30' north latitude, the southern boundary of Missouri, was established by the Missouri Compromise of 1820 as the northern limit of that part of the Louisiana Purchase that could be slave territory. Because of the Adams-Onís Treaty Texas was not considered a part of the Louisiana Purchase; therefore the annexation resolutions passed by Congress on February 28, 1845, included a restriction that if Texas were to be divided into more than one state, any state established north of the Missouri Compromise line (which was thus extended westward across Texas) would be a free state. In 1850, as a part of the Compromise of 1850 the northern boundary of the Texas Panhandle was fixed at the Missouri Compromise line, thus avoiding conflict in interpretations and making Texas clearly a "slave state." See also SLAVERY.
Don Edward Fehrenbacher, The South and Three Sectional Crises (Baton Rouge: Louisiana State University Press, 1980).