The U.S. Census Bureau's 2010 Summary File 1 (SF1) contains data from the 2010 decennial census. This data is collected via the so-called "short form", which all residents must complete by law. SF3 (the "long form") has been replaced by the American Community Survey (ACS); MCDC offers separate applications for browsing ACS data.
For some area types, the optional "Filter by county" selector will help limit the results.
Post-redistricting (2012 vintage) congressional districts, state legislative districts, and PUMA levels form a separate group that cannot be chosen in combination with other geographies. (They may be selected together.)
Choose "Advanced mode" for many more options, which will appear after submitting this form.
Additional tips are available by clicking the help icons () on the form.