Final answer:
Northerners had mixed feelings about the addition of new territory, with some celebrating the admission of California as a free state, while others opposed the expansion of slavery in the new territories.
Step-by-step explanation:
During the time period under consideration, northerners had mixed feelings about the addition of new territory. The admission of California as a free state in the Union brought joy to many northerners, as it represented a win for the anti-slavery movement. However, the issue of slavery in the newly acquired territories of New Mexico and Utah caused tension between the North and the South.
While southerners argued for the expansion of slavery in these territories, many northerners opposed this idea, fearing that it would further strengthen the political power of the slaveholding states and deprive small farmers in the West of opportunities. The debates over the expansion of slavery eventually led to the Compromise of 1850 and heightened sectional tensions that would eventually lead to the Civil War.