Programs filter based on geography, so the majority of your interviews will come from places in states surrounding your school or where you list your permanent address. Apply to all those, they will be the highest yield in terms of getting your application looked at. After that, it's hit or miss whether a program will even review your application. No program sits and looks at 1000 applications. They filter them down to a reasonable number based on geography and scores, then look at the applications from there.
Lets say you are from PA. You apply to all the PA programs, MD, WV, and a smattering of NY and Northeast programs. Lets say you apply to 30 programs. You'll probably get more than enough interviews with that strategy. But if you pick 30 programs that are all over the map of the US, with 5 in CA, 2 in Arizona, 10 in Florida, etc etc... you probably won't get nearly as many interviews and would have to apply to far more. Because programs in the SE are looking more apt to look at your app if you are from the SE. Programs out West are more likely to look at your app if you have a link to the west. Programs know students choose their residency largely based on their own geographic preferences. So programs use the students biases to try to maximize the number of "matchable" people on their list.
Apply smartly based on geography and you won't have to apply to 100 programs.
