Political map of North America & the Caribbean 13 May 1846 (Outbreak of the Mexican–American War): With the annexation of Texas, the US inherited that state's boundary dispute with Mexico. In a bid to settle the issue, as well as purchase the Mexican territories of Alta California and New Mexico (Santa Fe de Nuevo Mexico), President Polk (James K. Polk) offered to pay $25 million and forgive damages caused to US citizens in Mexico since independence (Mexican War of Independence). The Mexican government refused, prompting Polk to order troops to occupy the disputed land north of the Rio Grande (Nueces Strip). When Mexico responded by attacking this Army of Occupation (Thornton Affair), the US declared war (Mexican-American War).