The growth of sectionalism and slavery in the United States was significantly influenced by economic concerns. The North's embrace of industry and commerce led to dramatic economic differences between it and the agrarian South, whose economy was based on cotton and mainly on slavery. The Southern states became firmly committed to the system of slavery, which widened the gap between the slave-holding and the free states. Sectional tensions were also made worse by protective tariffs put in place to promote Northern businesses and discussions over the enlargement of territory. Despite the regions' economic interdependence, economic disparities and competing interests remained, eventually leading to the start of the American Civil War.