, Illinois Representative and future President, introduced this resolution in December 1847 to protest the U.S. war with Mexico. Although the United States admitted Texas as a state in 1845, the territory around the Rio Grande River along the border with Mexico continued to be disputed. On April 25, 1846, conflict between Mexican and U.S. troops erupted on land just north of the Rio Grande. President James K. Polk
used the incident to justify hostilities with Mexico, declaring in his war message to Congress that Mexico had “invaded our territory and shed American blood upon America's soil.” Many Representatives disapproved, arguing that the war was a means to extend slavery in the United States by increasing slave-holding territory. Nonetheless, Congress voted to declare war on Mexico on May 13. In this document, Representative Lincoln questioned President Polk’s justification, asking “whether the particular spot of soil on which the blood of our citizens
was so shed, was, or was not, our own soil
.” Congress did not pursue Lincoln’s questions, and the war ended with the Treaty of Guadalupe Hidalgo in 1848, and United States territorial expansion into what became New Mexico, Arizona, California, Nevada, Utah, and parts of Colorado and Wyoming.