•Why it earns a slot
Why it earns a slot: it invented the entire genre of comic-macabre frontier verse in one volume, and "The Cremation of Sam McGee" is still recited from memory by people who could not name the author.
A bank clerk who never mined an ounce of gold wrote the Yukon's defining ballads, and they run on saloon murders, a corpse in a boiler, and men the gold rush chewed up and spat out.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.