The Beginning of the Mexican War

Although Texas won independence from Mexico in 1836, Texas was still an independent country in 1844. In that year, James Polk ran for president promising to annex Texas. Polk won the election, which led to Congress voting to annex Texas before Polk even took office in 1845. Texas was now a state, but problems remained. Texans claimed that their state extended all the way to the Rio Grande River, while the traditional boundary of Texas was the Nueces River which was 150 miles North. Mexicans insisted that Texas’ border was the Nueces River.

President Polk wanted more than Texas, and he sent an ambassador to purchase California from Mexico. Mexico refused, and Polk planned for war. Polk sent American troops South of the Nueces River to the Rio Grande. Mexicans believed the army was invading their country, Polk and other Americans argued that the soldiers were still on American ground. On April 25, 1846, Mexican soldiers attacked part of the U.S. forces and killed 11 American soldiers. President James Polk immediately declared in a speech to Congress, “Mexico has passed the boundary of the United States, has invaded our territory, and shed American blood on American soil.”

Congress declared war. But not everyone agreed that the Mexican American War was a just war. A young Representative from Illinois, Abraham Lincoln made a speech known as the “Spot Resolution,” where Lincoln demanded that Polk prove that the “spot of soil” where blood was shed was actually American soil instead of Mexican land. Lincoln and many other Americans believed that the president had illegally picked a fight with Mexico in order to grab more land.