April 21, 753 BC (traditional date)
Romulus founds the city of Rome, kills his twin brother for making fun of it, then names the city after himself
According to tradition, Romulus and his twin brother Remus were born to a Vestal Virgin/daughter of a king and the war god Mars. Her brother, fearing the boys would have a stronger claim to his father’s throne, left the twins to die in the Tiber river. The river carried them safely to a she-wolf who suckled them, a woodpecker who fed them, and a shepherd and his wife who took them in.
Eventually the boys grew up and discovered their heritage, killed their uncle to return power back to their grandfather. They declined the crown from their homeland, and set out to found their own city.
The brothers squabbled over which hill to build the city, and when Romulus decided upon Palatine Hill, Remus continuously belittled the construction. He went so far as to jump over the city’s walls in jest, enraging Romulus further. According to one tradition, Romulus attacked Remus for his insults, throwing a spade into Remus’ head. In all traditions, Romulus is mournful for his brother’s death, enough to give him full funeral rites, but not enough to name the city after his fallen brother and instead names it after himself.