The primary effect of manifest destiny is that the United States is a bi-coastal nation stretching more than 3,000 miles from Maine to California. Manifest destiny also displaced a lot of non-native people and created an expanse of roads and railroads that aided in the development of industry.
Scholars also argue that manifest destiny ultimately resulted in the American Civil War. Southern plantations owners were among the earliest proponents of manifest destiny and saw it not only as a way of finding more land to cultivate but a method of expanding slavery. The argument over which new states would be slave states and which would not was ultimately one of the primary causes of the southern secession. The battle of the North and South over control of the expanding railroad system, which aided in the rapid growth of industry in the United States, also ultimately contributed to the Civil War. There were also religious effects of manifest destiny. The general belief of those who supported the idea of manifest destiny believed that national expansion was actually willed by God. The fact that Americans were repeatedly able to defeat Native Americans, as well as Spanish and Mexican armies, in the quest westward helped seal into the minds of Americans that the United States was a nation favored and blessed by God.