Why wasn't the missouri compromise of 1820 enough to end tension between the north and south by the 1840s?

the north and south continued to fight over territory by the rio grande.

some new territories went both above and below the line of compromise.

all of texas would be a slave state, which went against the missouri compromise.

mexico had outlawed slavery, so the new land gained from them could not allow slavery.

Some new territories went both above and below the line of compromise.

Explanation:

The Missouri Compromise divided Northern and Southern states on the slaves issue. The compromised passed as law in 1820, it forbade slavery in Louisiana and it considered Missouri as a slave state. Anything north the 36/30 parallel was considered slave free.

However, since the state of Missouri was considered a slave state, the South had one state more than the North and it was considered that the slave states had more power, because a slave counted as 3/5 of a person.

Thomas Jefferson predicted that dividing the country between slave and slave free states would lead the country to civil war.