What caused the period of national harmony to end?

The period of national harmony, often referred to as the "Era of Good Feelings" following the War of 1812, ended primarily due to rising sectional tensions and political divisions. The Missouri Compromise of 1820 highlighted disputes over slavery and its expansion into new territories, exacerbating regional conflicts between the North and South. Additionally, economic challenges, such as the Panic of 1819, further fueled discontent and differing interests, leading to the re-emergence of partisan politics and the decline of a unified national sentiment.