Good questions. We asked for help for someone who specializes is history. Bill T. spends a lot of time at the National Archives doing research on people.
Most people have an urge to be remembered in future generations. People also like to remember their friends and relatives and so keep pictures, letters, things that were important to them and other memories.
In the case of explorers like Christopher Columbus. The fact that they were trying to discover new places in order to bring riches and knowledge to their country meant that they kept very accurate records. Records were also kept of them. Birth records are extremely important to historians.
People like Colonel John By were honoured for their accomplishments by having their portraits and likenesses made in stone and bronze statues. Even before the invention of the camera, artists were helping us remember what people looked like by leaving paintings and statues for us to look at.
In fact, we looked in the Compton's Encyclopedia for Christopher Columbus's birthday and this is what we found
"Early Life of Columbus
"The father of Columbus was Domenico Colombo, a wool weaver. He had his own business in the port city of Genoa, Italy. There Cristoforo was born in the late summer or early autumn of 1451. (English-speaking peoples have since changed the Italian form of his name to Christopher Columbus.)
Hmmmm, so much for good records. Happy birthday sometime in late summer or early fall.
Answer #% % filename Document9 page% % page 1 of% % numpages 1 % % date \@ "MMMM d, yyyy"March 18, 1995