What did the missouri compromise of 1820 accomplish?

 It kept the balance of power in the Senate equal between the slave states and free states.

Further detail:

The Missouri Compromise (1820) admitted Missouri into the Union as a slave state with Maine being added at the same time to keep the balance of slave and free states equal.  It also prohibited any future slave states north of the latitude line 36 1/2 degrees north of the equator in territories of the Louisiana Purchase, with the exception of Missouri (north of that line) being admitted as a slave state.  

in the united states, the president is controlled by the

constitution, and in all respects subordinate to it. insofar

as it deals with presidential power, however, the american

constitution has proved to be a highly malleable document.

with very few exceptions,' the constitutional provisions relating to the president have not been changed at all since

they were ratified in 1787. but in the late twentieth century, those provisions do not mean what they meant in

1787. the constitution is a legal document, and it is enforced judicially; but its meaning was hardly fixed when it

was ratified. in particular, the contemporary president has

far broader powers than the original constitution contemplated. it is remarkable but true that large-scale changes in

the authority of the president have been brought about

without changes in the constitutional text, but nevertheless

without significant illegality.

this is a paradox. is it not clear that constitutional

changes, if not textual, are illegal? the paradox has considerable relevance to our current thinking about the presidency in particular and about constitutionalism in general.

perhaps the framers of the american constitution feared

legislative power most of all; 2 but from well-known events

in the twentieth century, it is possible to conclude that it is

presidential power that holds out the greatest risks to both

liberty and democracy. the president is by far the most visible leader in the nation; he is often the only person in government with a national constituency. moreover, he is

“i think it is very plausible that if there are five votes to end the death penalty, it could be with the people who are on the court right now,” - smith

so basically it is not clearly and consistently imposed