Roper Center for Public Opinion Research
The Roper Center for Public Opinion Research at Cornell University is the world's oldest archive of social science data and the largest specializing in data from public opinion surveys. Its collection includes over 27,000 datasets and more than 855,000 questions with responses in Roper iPoll, adding hundreds more each year.
Source: Wikipedia — Roper Center for Public Opinion Research (CC BY-SA 4.0)