The river, down

Looking for the origin of this phrase......believe that it is distinct from "sold down the river" and may have something to do with being sent to prison e.g to Sing Sing from New York City.

Thank you!-)

SELL DOWN THE RIVER - "To betray someone. The saying originated in the southern states of the United States and was used in connection with the illegal slave trade after 1808. The South and Southwest cotton and sugar businesses were booming, and slaves from the upper South were bought, transported down the Mississippi River and sold at the markets of Natchez or New Orleans." From the Random House Dictionary of Popular Proverbs and Sayings by Gregory Y. Titelman (Random House, New York, 1996).

Back in a mo'.