Question: which territory was adjacent to the slave state of missouri

title: Missouri Compromise
text: To balance the number of `` slave states '' and `` free states '' , the northern region of what was then Massachusetts , the District of Maine , ultimately gained admission into the United States as a free state to become Maine . This only occurred as a result of a compromise involving slavery in Missouri , and in the federal territories of the American West . The admission of another slave state would increase the South 's power at a time when northern politicians had already begun to regret the Constitution 's Three - Fifths Compromise . Although more than 60 percent of whites in the United States lived in the North , by 1818 northern representatives held only a slim majority of congressional seats . The additional political representation allotted to the South as a result of the Three - Fifths Compromise gave southerners more seats in the House of Representatives than they would have had if the number was based on just free population . Moreover , since each state had two Senate seats , Missouri 's admission as a slave state would result in more southern than northern senators . A bill to enable the people of the Missouri Territory to draft a constitution and form a government preliminary to admission into the Union came before the House of Representatives in Committee of the Whole , on February 13 , 1819 . James Tallmadge of New York offered an amendment , named the Tallmadge Amendment , that forbade further introduction of slaves into Missouri , and mandated that all children of slave parents born in the state after its admission should be free at the age of 25 . The committee adopted the measure and incorporated it into the bill as finally passed on February 17 , 1819 , by the house . The United States Senate refused to concur with the amendment , and the whole measure was lost .