As I mentioned yesterday, there's a new survey aimed at determining patterns of gun ownership and defensive gun use, from Prof. William English at the Georgetown University. It's much larger than most other such surveys, with over 54,000 adult American respondents, of whom over 16,700 personally owned guns.
The large sample allows the survey to give much more reliable information about subcategories of the U.S. population, for instance getting a sense of gun ownership rates by state (ranging from 16%, or about half the national level, in Massachusetts, to 54%, or more than half above the national level, in Idaho).
My own California, generally seen as a state with very heavy gun regulations, is still not far below the average, at 25%. Even deepest-of-deep-blue D.C. is at 24% (though with a higher margin of error, 16% to 35%).