guys jokes aside this river was actually a key point in the civil war, where Ulysses S. Grant was able to sever the confederate supply train through the Mississippi, while the Union was suffering through high prices of supplies through inflation. If you want to learn more about this, just search up Big Black inflation

as soon as you said key point in civil war I KNEW the punchline was gonna be big black ___
gang this is in northern maine

no, like there's actually a river in Mississippi called the big black river