Hard to say which research organizations were specifically mentioned in the unit you took with your teacher, so we'll trust the other respondent here that says it was Harris and Gallup.
Pew is a research organization also. The Census is not -- that's a US government function conducted every 10 years.
Let me give you some detail about each of the research organizations. I'll do so in alphabetical order.
Gallup, Inc. was founded by George Gallup in New Jersey in 1935, then called The American Institute of Public Opinion. Current headquarters of the Gallup organization are in Washington, DC, with over 30 offices located around the world. Gallup says that it "delivers analytics and advice to help leaders and organizations solve their most pressing problems," and claims that it "has more data and insights on the attitudes and behaviors of employees, customers, students and citizens than any other organization in the world."
Harris Insight & Analytics, headquartered in Rochester NY, conducts The Harris Poll, which was begun in 1963. The Harris Poll describes itself (on its website) as "one of the longest running surveys in the U.S. tracking public opinion, motivations and social sentiment." The stated mission of The Harris Poll is "to reveal the authentic values of modern society to inspire leaders to create a better tomorrow."
Pew Research Center, established in 2004, is headquartered in Washington DC. The Pew Research Center describes itself as "a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping the world." Pew Research conducts "public opinion polling, demographic research, content analysis and other data-driven social science research."
