With the capture of Pensacola, Jackson established de facto American control of the entire territory. While Monroe supported Jackson's actions, many in Congress harshly criticized what they saw as an undeclared war. With the support of Secretary of State Adams, Monroe defended Jackson against domestic and international criticism, and the United States began negotiations with Spain.[114][115][113]
Spain faced revolt in all of its American colonies and could neither govern nor defend Florida. On February 22, 1819, Spain and the United States signed the Adams–Onís Treaty, which ceded the Floridas in return for the assumption by the United States of claims of American citizens against Spain to an amount not exceeding $5,000,000. The treaty also contained a definition of the boundary between Spanish and American possessions on the North American continent. Beginning at the mouth of the Sabine River the line ran along that river to the 32nd parallel, then due north to the Red River, which it followed to the 100th meridian, due north to the Arkansas River, and along that river to its source, then north to the 42nd parallel, which it followed to the Pacific Ocean. 