United States History On This Date: May 13th

1846 — U.S. declares war on Mexico officially enacted — Following congressional approval, President James K. Polk signed the formal declaration of war against Mexico. The conflict accelerated debates over expansion, slavery, and national destiny. Within two years, the United States would acquire vast western territories, reshaping the political balance and intensifying sectional tensions that would erupt into the Civil War.

1862 — New Orleans placed under Union administration — Two weeks after its capture, Union General Benjamin Butler formally assumed control of New Orleans, the largest city in the Confederacy. His strict policies, including sanitation reforms and controversial enforcement measures, sparked outrage across the South. The occupation demonstrated the Union’s growing dominance along the Mississippi and dealt a major psychological blow to Confederate hopes.

1917 — Selective Service Act passes Congress — As the United States mobilized for World War I, Congress approved the Selective Service Act, authorizing a national draft to raise a modern army. The law transformed federal authority over military manpower and reshaped American society as millions of men registered for service. It also marked a turning point in the nation’s commitment to the Allied war effort.

1958 — U.S. launches Explorer 1 successor satellite — Building on the success of Explorer 1, the United States continued its early space program with additional scientific satellites designed to study cosmic radiation and Earth’s magnetosphere. These missions expanded understanding of the Van Allen belts and strengthened America’s position in the emerging space race. The Explorer series became a cornerstone of early U.S. space science.

Artist Impression of Explorer I Satellite In Orbit