In "Life on the Mississippi", beginning Chapter VIII, (first sentence, in
fact), Twain wrote the word points in quotes, like this:

'...I managed to pack my head full of islands, towns, bars, "points", and
bends;"

Does anyone have any ideas as to why he quoted the word "points"? What was a
"point" that he refers to? It seems as though he's suggesting that so-called
"points" weren't really as easily identifiable as say a town, bar, or
island.

In addition, what was a "Crossing"? Is a Crossing a Point?