On February 23, 1945:

During the bloody Battle for Iwo Jima, U.S. Marines from the 3rd Platoon, E Company, 2nd Battalion, 28th Division take the crest of Mount Suribachi, the island's highest peak and most strategic position, and raised the U.S. flag.

On April 12, 1861:

The bloodiest four years in American history begin when Confederate shore batteries under General P.G.T. Beauregard open fire on Union-held Fort Sumter in South Carolina's Charleston Bay. During the next 34 hours, 50 Confederate guns and mortars launched more than 4,000 rounds at the poorly supplied fort. On April 13, U.S. Major Robert Anderson surrendered the fort. Two days later, U.S. President Abraham Lincoln issued a proclamation calling for 75,000 volunteer soldiers to quell the Southern "insurrection."

According to tradition, on April 21, 753 B.C., Romulus and his twin brother, Remus, found Rome on the site where they were suckled by a she-wolf as orphaned infants. Actually, the Romulus and Remus myth originated sometime in the fourth century B.C., and the exact date of Rome's founding was set by the Roman scholar Marcus Terentius Varro in the first century B.C.

On April 22, 1970:

The first "Earth Day" was observed.

Nice remember too !