Population data can used for numerous purposes. One can look at the most recent data to provide a snapshot of what an area is like- how many people live in an area, the racial, ethnic, gender, and age breakdown, along with economic and social overviews of an area. One can look at older data to both see what a place was like at a certain time and to track changes over time.
The U.S. Census Bureau's data is a very good place to go to get such data. The decennial counts have been going on since 1790, when the Constitution mandated that it be done to decide how many members of Congress each state would get. With the rise of statistical sampling and the social sciences, the work of the Census Bureau has evolved to the point where they are taking annual measurements through the American Community Survey in addition to the counting of everyone every 10 years.
This guide exists to help you navigate the various resources that exist to see population data. Our emphasis is on Boston, but some of the information can be of assistance for research beyond.