• CDs-by-County: I think you’re all going to love this. Thanks to yet more hard work by jeffmd, we now have a new chart for you: congressional districts by county. Click the link and you’ll find a tab for each state laying out which counties are in which congressional district. But there’s a lot more. Jeff has also figured out how many people in each county (or part thereof) are in a given district (that’s column C), what percentage of each CD is made up by each county or county-part (column D), and finally, what percentage of each county is in a given CD (column E). Since counties are an easily understood and frequently used layer of political organization (for example, party endorsements are often made at the county level), this kind of information is very useful, since it lets you see how much sway a particular county has in a particular congressional district.
For instance, if you open the Arizona tab, you’ll see that 197,708 residents of Pinal County live in AZ-01, and those folks in Pinal make up almost 28% of the congressional district’s total population. But if you look at column E, you’ll see that only 53% of Pinal is place inside the 1st—that means its split among more than one district. Scrolling down (or searching on the word “Pinal”), you’ll see that there’s also a teeny-tiny fraction of the county in AZ-03 (just 545 people), as well as a much bigger chunk (some 177K) in AZ-04.
Source: Daily Kos