Final answer:
The conflict over territorial concern during early US westward expansion was predominantly about whether new states would permit slavery. The issue of slavery's expansion became a pivotal aspect that influenced political debates, and sectional tensions, and ultimately played a significant role in leading to the Civil War.
Step-by-step explanation:
The addition of US states with westward expansion in the early 1800s led to conflict over the territorial concern of whether slavery would be allowed in the new territories. This question derives from the contentious issue of whether expansion westward should include the expansion of slaveholding states, a debate that deeply influenced U.S. domestic policy and was a principal factor in the political and social tensions of the time. The concept of Manifest Destiny encouraged the belief that the United States was preordained to expand its territories, and with it, the American way of life. However, the moral implications and the balance of power between free and slave states caused heated debates, culminating in a series of compromises and acts that sought to address the issue, such as the Missouri Compromise of 1820, the Compromise of 1850, and the Kansas-Nebraska Act of 1854. These compromises, however, were ultimately unsuccessful in preventing the escalation of tensions that led to the American Civil War.