In 1860 the county seat was moved to Cairo, Illinois, at the confluence of the Ohio and Mississippi rivers.

Legend holds that Dred Scott, a slave whose freedom suit reached the Supreme Court, may have been imprisoned in the local courthouse jail for a time while his case was heard.

He had claimed freedom after being held in a free state but, setting aside decades of precedent, the US Supreme Court held that African Americans had no rights under the constitution, and slaves had no standing to sue for freedom (see Dred Scott v. Sanford).

As the Mississippi River at Thebes is more than four feet deep, the town became a busy steamboat port.

Union troops passed through Thebes on their way to attack the South during the American Civil War.

In 1923, Thebes elected a woman Nora Gammon to the mayorship and an all-woman slate of alderman, running on a law enforcement platform.

[6] In literature, Thebes is the home village of Captain Andy Hawks, his wife Parthenia Ann Hawks, and daughter Magnolia in the Edna Ferber novel Show Boat (1926).

15.44% of all households were made up of individuals, and 6.62% had someone living alone who was 65 years of age or older.