Gallup was born into a poor farming family in Jefferson, Iowa. He entered Iowa State University and produced a doctoral thesis entitled A New Technique for Objective Methods for Measuring Reader Interest in Newspapers. In 1935 he founded the American Institute of Public Opinion. In 1936 the organisation achieved fame by correctly predicting, from the replies of only 50,000 respondents, the result of the presidential election, in contradiction to the widely respected Literary Digest magazine whose much more expensive random telephone poll of two million people got the result wrong.
Gallup died in Switzerland. The worldwide Gallup Organization that he founded is now run by his son George Gallup Jr.