The Ostend Manifesto was part of an attempt to add Cuba to the US. Southerners wanted an aggressive policy with Spanish-ruled Cuba, by having the island become a possible
…new slave state. In October 1854, three Americans "one of which was the American minister to Spain, Pierre Soule' of Louisiana" composed a document on Cuba and called it the Ostend Manifesto, claiming the island belonged "naturally to the great family of the states...". Also stating that Spain's control of Cuba was unnatural. The United States offered to buy Cuba from Spain but if Spain refused to sell, the document warned, "by every law, human and Divine, we shall be justified in wresting it from Spain". (in other words... give us Cuba or else) The opinion of making a war with Spain over this was a secret memorandum to US President Pierce from his envoys in Europe. The incident split the Democratic Party & embarrassed President Pierce, so he repudiated it, and thus it ended. The Ostend Manifesto caused a great uproar and embarrassed President Franklin Pierce's administration, after it became public. Other nations denounced it and it had similar reactions in the US. Many in the North was angered that the South was willing to provoke war with Spain to extend more slave holding states. Cuba had legal slavery and US envoys had offered as much as $100 million for the purchase. (MORE) 
