There are certain pockets of the country which are very competitive, due to a number of reasons. Keep in mind that congressional districts generally have around the same amount of people, so it really has more to do with demographic and then whatever special reason might draw kids towards being an officer in the military; typically a family member being in the military.
As far as demographics, it seems to me that Suburban areas, as opposed to either rural or urban areas, draw the most applicants and interest in the academies. I can make surmisions about that, but in general suburban areas are more affluent, parents tend to have a higher education themselves, and therefore value college and top colleges in particular, and when that is the case there are more kids applying to all top schools, including the academies.
When there is a significant military presence in an area there will be more interest in the Academies, because military families are very familiar with the benefits of attending an Academy, whereas the general population is far less in touch with academies, how they work, what the deal is, and the long-term benefits.
Beer is in the Northeast part of the country, the North West, it in particula Northern Virginia, where those factors are particularly strong, have tons of applicants, and are extremely competitive.
Most large metropolitan areas have a lot of applicants, but are not necessarily extremely competitive;at least as compared to those other areas referenced above. Any given year though a moderately competitive district can be either highly competitive, or not very competitive at all. Depends on interest and the draw that particular year. Nothing should ever be taken for granted in this process.