Organized labor is an association that engages in collective bargaining to improve workers' economic status and working conditions. In most countries, the union formation process is regulated by a government agency, such as the National Labor Relations Board (NLRB) in the United States
From what google is telling me. It is about primary and secondary source.
Southern Democrats favored westward expansion, partly to expand cotton plantations and slavery into the west, however, the Whigs were worried about expanding slavery into the west. Most Democrats were in favor of expanding, because it would make America larger. The Whigs, however, were worried about losing representation in the Congress.