David Dunn was born in Cornish (in modern-day Maine, then a part of Massachusetts) on January 17, 1811.

Dunn studied law under then future Governor, "Squire" John Fairfield, of Saco.

The game of political musical chairs continued with Dunn resigning and the new President of the Senate, John W. Dana, acting as Governor until newly elected Hugh J. Anderson was sworn in.

In 1845 Dunn was elected to the Maine Senate and served as its President following the resignation of Stephen Chase of Fryeburg in 1846.

Dunn was rewarded for his tenacity by the Buchanan administration which appointed him to a Clerkship in the Post Office in Washington, D.C., which he held from 1857 to 1861.