This service and his law experience helped to win him election to the 13th Congress of the United States in 1812.

On April 17, 1822, President James Monroe appointed him as the first non-military governor of the territory, succeeding Gen. Andrew Jackson.

During his twelve-year administration, he selected the small Indian village of Tallahassee as the site for the territory's capital, on account of its (north) central location.

He signed the first act of legislation in the Territory of Florida, dividing it into four sections and establishing the local court system.

William Pope Duval died in Washington, D.C.; his remains were interred at the Congressional Cemetery.