As Speaker of the House of Representatives (1811–14) he played a central role in the agitation leading to the War of 1812, and was one of the commissioners responsible for the negotiation of the Treaty of Ghent that ended it. He was one of the architects of the Missouri Compromise and won support for his American System, a policy to improve national unity through a programme of economic legislation. His final political achievement lay in helping the passage of the Compromise of 1850 between the opposing Free-Soil and pro-slavery interests. His role in arranging major sectional compromises between North and South (1820, 1833, and 1850) earned him the title of ‘the Great Compromiser’.