Who became president in 1845 with plans to expand american territory?

The president who had those ideas was James K. Polk. When he was the president, he reduced tariffs, reformed the national banking system and settled a boundary dispute with the British that secured the Oregon Territory for the United States. Polk also led the nation into the Mexican-American War (1846-48), which the United States acquired California and much of the present-day southwest. It should also be mentioned that during his tenure, America's territory grew by more than one-third and extended across the continent for the first time.

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