December 30 · This Day in America
In Mexico City, U.S. minister James Gadsden and representatives of Santa Anna sign a treaty selling the United States roughly 30,000 square miles of desert south of the Gila River — the country that would become southern Arizona and New Mexico. The price was set at ten million dollars; the real object was a flat, snow-free route for a southern transcontinental railroad. With this last stroke of the pen the contiguous map of the United States is, at last, complete — the final piece of the lower forty-eight. Everything after this is not acquisition but argument: over the railroad, over slavery's reach, over what kind of country would be laid across all that finished ground. The continent stops growing here. The harder question of what to do with it begins.
Source: www.archives.gov
Also on this day · 1924
An American astronomer named Edwin Hubble reports that faint stars he measured in the Andromeda nebula lie far beyond the Milky Way — meaning Andromeda is not a cloud in our galaxy but a separate galaxy entirely. In a single result, the cosmos goes from one galaxy to countless. Humanity's address gets a great deal larger that day, and we are suddenly very small and very lucky to be looking.
Source: science.nasa.gov