1804: Louisiana Purchase: St. Louis holds a ceremony that officially marks the transfer of ownership of the land known as the Louisiana Purchase from France to the United States. The dates of March 9 and 10 are commemorated as Three Flag Day because the area had within the course of two years been under Spanish, French, and then, finally, American control. Several months later, Lewis and Clark went forth on their famous expedition.
1848: Treaty of Guadalupe-Hidalgo: The Mexican-American war is officially over after the two countries ratify the treaty. This treaty resulted in the current borders we know today, with the Rio Grande as the main dividing line. All or parts of Texas, California, New Mexico, Arizona, Nevada, Utah, Oklahoma, Kansas, Colorado and Wyoming were once part of Mexico, and between 1850 and 1912, all of these became states. Residents of these territories would choose to American citizenship or to return to what remained of Mexico. Ninety percent chose American citizenship.
1876: You have a phone call: Alexander Graham Bell made the first successful telephone call, where he reportedly said to his assistant, “Mr. Watson, come here, I want to see you.” This marked the beginning of telephone communication, where for the first time, people could communicate across distances in real time. But the invention was not without controversy, and some claim that the real inventor of the telephone was actually Bell’s rival, Elisha Gray.
1969: A killer confesses: Almost a year prior, on April 4, 1968, James Earl Ray assassinated Martin Luther King on the balcony of a Memphis motel. He fled to Canada and later to the UK under a false name, but was later extradited back to Tennessee. He plead guilty to killing Dr. King on his 41st birthday, but he later retracted his guilty plea. He escaped prison in 1977 and was captured two days later.
2006: A trip to Mars: The Mars Reconnaissance Orbiter arrives at the planet Mars. It was launched August 12 of 2005, and made it to Martian orbit seven months later, March 10. It remains there, monitoring weather patterns, ice and landforms, and has sent back more data to Earth than all previous missions combined.