Summary: The north and south were having political rivalries on whether slavery should be abolished or kept. Henry Clay wrote the Missouri Compromise hoping it would not only resolve the issue of slavery but would also lead to the United States having an equal number of free states and slave states. The north and south both agreed with the terms of the Missouri Compromise which included regulating slavery in western territories, forbidding slavery in Louisiana and any territory that came with the Louisiana Purchase ( Arkansas, Iowa, Missouri, Kansas, Oklahoma, and Nebraska, parts of Minnesota and Louisiana west of Mississippi River, including New Orleans, big parts of North and northeastern New Mexico, South Dakota, northern Texas, some parts of Wyoming, Montana, and Colorado as well as portions of Canadian provinces Alberta and Saskatchewan), and slavery was forbidden anywhere north of the 36/30 parallel territory except Missouri where it had been considered a slave state. This Act stayed in place until the Kansas-Nebraska Act was put into place. Since the Kansas-Nebraska act forbade the terms and conditions that came with the Missouri Compromise that led to many disputes between the north and the south.
Northern Perspective: The northerners found the Missouri Compromise was unfair because the south had one extra state than them (Missouri), and they thought the south was favored more and had more power and control over them when the Kansas-Nebraska Act was put into place.
Southern Perspective: The southerners liked the Missouri Compromise but they still wanted more power and control over the north, so when the Kansas-Nebraska Act was put into place they got all the power and control they needed to use on the northerners.