The Missouri Compromise was passed in 1820. It was between people who believed in pro-slavery and anti-slavery in the United States. The Missouri Compromise took place when John Monroe was president. In 1819 the people of Missouri territory requested Missouri to be a slave state which messed up the balance between free states and slave states in the US. Congress decided to make a compromise that granted Missouri’s request but also made Maine a free state out of the territory of northern Massachusetts. It also passed an amendment that split across the Louisiana territory making a boundary of free and slave territory for future western states. The Missouri compromise decided everything north of the 36, 30 parallel line, except Missouri, would be free states or territories, everything south would be open to slavery.
This compromise was an effort to keep balance of power in the slave and free states. It was the first real attempt to end slavery in the United States. The Missouri Compromise lasted for three decades and kept the slavery issue from leading to war. The Missouri Compromise only delayed what was bound to happen sooner or later; the Civil War. Thomas Jefferson was afraid that the crisis in Missouori would lead to Civil War; it did eventually but it took 40 more years.
I think the Missouri Compromise was a pretty fair compromise. It was an attempt to limit spread of slavery in the US. It lasted until the California gold rush and the Compromise of 1850 when new territory had just been won from Mexico.
http://www.history.com/topics/missouri-compromise
http://history1800s.about.com/od/slaveryinamerica/a/missouricompro.htm