On this day in 1811, American fur traders arrived at the mouth of the Columbia River to found Fort Astoria. The American settlement itself was short-lived; British traders took possession during the War of 1812. Without the precedent it established, however, Oregon, Washington and Idaho might well be Canadian provinces.
On this day in 1861, Confederate forces launched an attack upon the Union's Fort Sumter in Charleston Harbor. The Civil War was officially underway.
On this day in 1961, the Soviets launched Yuri Gagarin into space -- yet another thorn in the side of a United States still irked by the Soviets' launch of Sputnik in 1957. Fortunately, 24 days later (May 5) Alan Shepard successfully made it into orbit.
On this day in 1981, the first American space shuttle--the Columbia--was launched. The shuttle program comes to an end later this year.