The birth and death place of David Gallup are not known. Also give about his youth and schooling, as well as his career beyond politics, the sources do not shed. He lived in Plainfield in Hartford County and joined the Republican Party. In May 1860 he was a delegate to the Republican National Convention in part in Chicago, was nominated on the Abraham Lincoln as a presidential candidate. In 1866 he was a member and President of the House of Representatives from Connecticut; in 1869 he was a member of the State Senate.
In 1878, Gallup was elected on the side of Charles B. Andrews as Vice- Governor of the State of Connecticut. This post he held 1879-1881. Yet he was Deputy Governor and Chairman of the State Senate. He died on August 15, 1883.