Each group that held sway over a particular strip of the Mississippi River controlled who used it.
2.
to have great influence.
Ten years after she correctly predicted the crash, she still holds sway among stock brokers.
hold sway (over someone)
To have or exert great control or influence (over someone). My father retired from politics years ago, but he still holds sway in the town to this day.It is suspected that the president's wife holds a lot of sway over the administration's policy.
hold ˈsway (over somebody/something)
(literary) (of a person, a movement, an idea, etc.) have power, control or great influence over somebody/something: Rebel forces hold sway over much of the island.These ideas held sway for most of the century.