Which force, westward expansion or the North-South division, was a stronger factor shaping the development of the British North American colonies and the United States between 1607 and 1877?

The greater force in shaping the development of the United States was the North-South division. In the colonial period and early Republic, the regional development of states determined the nature and outcome of important questions in American life. One of the most important was how representation was determined in the Congress. The growing and increasingly powerful institution of slavery in the South meant that population in the Southern states outstripped the numbers in the North. In order to deal with this situation, enslaved populations in the South were counted as three fifths for representation in the House of Representatives. The North-South division also led to the debate over slavery's expansion that dominated the first half of the nineteenth century. These debates led to the Missouri Compromise of 1820, the Compromise of 1850, the Fugitive Slave Law, the Kansas-Nebraska Act of 1854 and the Dred Scott Decision in 1857 and the Civil War (1861-1865) and Reconstruction (1865-1876).