As a young man he moved to Cloverport, Kentucky, on the Ohio River and became a prosperous merchant.

He married Polly Moorman in 1826 and the couple had several children before moving to Henderson, Texas, in 1844.

When Texas was readmitted to the Union, the legislature named him, along with Morgan Hamilton, to the U.S. Senate.

[1][2] After his Senate term, Flanagan took up residence on one of his farms near Longview, Texas.

Flanagan died on his farm in Longview in 1887 and was buried next to his first wife, Polly, in their family graveyard in Henderson, Texas.