The President who purchased Florida for the United States was James Monroe. The acquisition of Florida, known as the Adams-Onís Treaty, was a significant diplomatic achievement during Monroe's presidency and contributed to the expansion of U.S. territory in the early 19th century.

The Adams-Onís Treaty, negotiated between the United States and Spain, was signed on February 22, 1819, during Monroe's administration. The treaty addressed several territorial disputes and boundary issues between the two nations. One of the key provisions of the treaty involved the cession of Florida from Spain to the United States.

The acquisition of Florida was important for several reasons:

1. Border Clashes: The region had been a source of tension between the United States and Spain due to border clashes, incursions by Native American tribes, and the presence of fugitive slaves and Seminole Indians in Florida.

2. Westward Expansion: The acquisition of Florida was aligned with the broader trend of westward expansion in the United States. The region's strategic location and fertile land made it appealing for settlement and economic development.

3. Naval Control: The control of Florida allowed the United States to gain dominance over important ports and waterways, including the Gulf of Mexico and access to the Atlantic Ocean.

4. Resolution of Disputes: The treaty also resolved other boundary issues, such as defining the western boundary of the Louisiana Purchase and clarifying the border between Spanish Mexico and the United States.

The Adams-Onís Treaty was ratified by both the United States Senate and the Spanish government in 1821, and Florida officially became a U.S. territory. This acquisition set the stage for Florida's eventual statehood in 1845. The treaty demonstrated Monroe's commitment to expanding U.S. territory, resolving border conflicts, and securing strategic interests in the southeastern United States.

In conclusion, President James Monroe played a crucial role in acquiring Florida for the United States through the Adams-Onís Treaty. This diplomatic achievement not only resolved territorial disputes but also paved the way for the growth, development, and eventual statehood of Florida within the United States.