I’ve known rivers ancient as the world and older than the flow of human blood in human veins. (2-3)
Memory is a human thing, right? Without humans, can there be memory? Our speaker connects himself to something that is before human memory and history. He connects himself to the bedrock and foundation of civilization.
I bathed in the Euphrates when dawns were young. (5)
Not only does our speaker know old rivers, but he grew up with them too. He was around at the birth of civilization in Mesopotamia.
I built my hut near the Congo and it lulled me to sleep. (6)
Our speaker is not a god or a divine creature. He is distinctly human and he does things like bathe, build, and sleep.
I looked upon the Nile and raised the pyramids above it. (7)
The pyramids are one of the seven wonders of the world. Whenever we see a picture of them, we immediately known what they are – they are that embedded in our imagination and in our memories. When we think back to ancient Egypt, perhaps we think about people like Cleopatra, King Tut, or other famous royal people. In this line, however, we hear the unique perspective of a peasant, of someone who actually helped to build the pyramids (rather than order them to be built). We get a different historical perspective.
I heard the singing of the Mississippi when Abe Lincoln went down to New Orleans, and I’ve seen its muddy bosom turn all golden in the sunset. (8-10)
Here, our speaker invokes a corner of history that we don’t always read about. We know Abe Lincoln delivered the Emancipation Proclamation and successfully abolished slavery during his presidential term. In this line, we are reminded of how powerful memory is, and how events can seem more magical in our remembering of it than perhaps they really are. Our speaker’s memory involves a river that sings and that transforms into gold. The poem has a magical, mystical quality in this way.